Tests fail with LTO due to ODR / type mismatch violations

I tried to build with the following *FLAGS to optimize the build: `-flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing`

Link-Time Optimization is a massively global compiler optimization pass which is pretty handy for producing faster executables. It also has the interesting property that because the compiler does whole-program analysis using bytecode, it can save type information and perform error checks that it normally doesn’t have enough insight for. In particular, checking for ODR issues and checking function type signature mismatches.

Note that *all* the -Werror=* flags are used to help detect cases where the compiler tries to optimize by assuming UB cannot exist in the source code -- if it does exist, ordinarily the code would be miscompiled, and this says to make the miscompilation a fatal error.

I got this error:
```
gcc.link ../../../bin.v2/libs/smart_ptr/test/abi_test_mt_nt.test/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden/abi_test_mt_nt

"x86_64-pc-linux-gnu-g++" -Wl,-rpath -Wl,"/var/tmp/portage/dev-libs/boost-1.89.0/work/boost_1_89_0-abi_x86_64.amd64/bin.v2/libs/atomic/build/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden" -Wl,-rpath-link -Wl,"/var/tmp/portage/dev-libs/boost-1.89.0/work/boost_1_89_0-abi_x86_64.amd64/bin.v2/libs/atomic/build/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden" -o "../../../bin.v2/libs/smart_ptr/test/abi_test_mt_nt.test/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden/abi_test_mt_nt" -Wl,--start-group "../../../bin.v2/libs/smart_ptr/test/abi_test_mt_nt.test/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden/abi_test_main.o" "../../../bin.v2/libs/smart_ptr/test/gcc-14.3/gentoorelease/x86_64/link-static/pch-off/threading-multi/visibility-hidden/libabi_test_nt.a" "../../../bin.v2/libs/atomic/build/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden/libboost_atomic.so.1.89.0" "../../../bin.v2/libs/atomic/build/gcc-14.3/gentoorelease/x86_64/link-static/pch-off/threading-multi/visibility-hidden/libboost_atomic.a" -Wl,-Bstatic -Wl,-Bdynamic -lrt -Wl,--end-group -fPIC -m64 -pthread -fvisibility=hidden -fvisibility-inlines-hidden -Wl,-O1 -Wl,--as-needed -Wl,-z,pack-relative-relocs -flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing -Wl,--defsym=__gentoo_check_ldflags__=0

../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:70:28: error: type ‘struct sp_counted_base’ violates the C++ One Definition Rule [-Werror=odr]
70 | class BOOST_SYMBOL_VISIBLE sp_counted_base
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:38:28: note: a different type is defined in another translation unit
38 | class BOOST_SYMBOL_VISIBLE sp_counted_base
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:77:27: note: the first difference of corresponding definitions is field ‘use_count_’
77 | boost::uint_least32_t use_count_; // #shared
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:45:26: note: a field of same name but different type is defined in another translation unit
45 | boost::int_least32_t use_count_; // #shared
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:70:28: note: type ‘uint_least32_t’ should match type ‘int_least32_t’
70 | class BOOST_SYMBOL_VISIBLE sp_counted_base
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:86:10: error: type of ‘release’ does not match original declaration [-Werror=lto-type-mismatch]
86 | void release() noexcept
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:116:10: note: ‘release’ was previously declared here
116 | void release() // nothrow
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:116:10: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:100:10: error: type of ‘weak_release’ does not match original declaration [-Werror=lto-type-mismatch]
100 | void weak_release() noexcept
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:130:10: note: ‘weak_release’ was previously declared here
130 | void weak_release() // nothrow
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:130:10: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:65:18: error: type of ‘destroy’ does not match original declaration [-Werror=lto-type-mismatch]
65 | virtual void destroy() noexcept // nothrow
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:97:18: note: ‘destroy’ was previously declared here
97 | virtual void destroy() // nothrow
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:97:18: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
lto1: some warnings being treated as errors
lto-wrapper: fatal error: /usr/bin/x86_64-pc-linux-gnu-g++ returned 1 exit status
compilation terminated.
/usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../x86_64-pc-linux-gnu/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
...skipped abi_test_mt_nt.run for lack of abi_test_mt_nt...
common.mkdir ../../../bin.v2/libs/smart_ptr/test/get_deleter_test2_no_rtti.test

mkdir -p "../../../bin.v2/libs/smart_ptr/test/get_deleter_test2_no_rtti.test"

gcc.link ../../../bin.v2/libs/smart_ptr/test/abi_test_nt_mt.test/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden/abi_test_nt_mt

"x86_64-pc-linux-gnu-g++" -Wl,-rpath -Wl,"/var/tmp/portage/dev-libs/boost-1.89.0/work/boost_1_89_0-abi_x86_64.amd64/bin.v2/libs/atomic/build/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden" -Wl,-rpath-link -Wl,"/var/tmp/portage/dev-libs/boost-1.89.0/work/boost_1_89_0-abi_x86_64.amd64/bin.v2/libs/atomic/build/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden" -o "../../../bin.v2/libs/smart_ptr/test/abi_test_nt_mt.test/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden/abi_test_nt_mt" -Wl,--start-group "../../../bin.v2/libs/smart_ptr/test/abi_test_nt_mt.test/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden/abi_test_main.o" "../../../bin.v2/libs/smart_ptr/test/gcc-14.3/gentoorelease/x86_64/link-static/pch-off/threading-multi/visibility-hidden/libabi_test_mt.a" "../../../bin.v2/libs/atomic/build/gcc-14.3/gentoorelease/x86_64/pch-off/threading-multi/visibility-hidden/libboost_atomic.so.1.89.0" "../../../bin.v2/libs/atomic/build/gcc-14.3/gentoorelease/x86_64/link-static/pch-off/threading-multi/visibility-hidden/libboost_atomic.a" -Wl,-Bstatic -Wl,-Bdynamic -lrt -Wl,--end-group -fPIC -m64 -pthread -fvisibility=hidden -fvisibility-inlines-hidden -Wl,-O1 -Wl,--as-needed -Wl,-z,pack-relative-relocs -flto=4 -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing -Wl,--defsym=__gentoo_check_ldflags__=0

../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:38:28: error: type ‘struct sp_counted_base’ violates the C++ One Definition Rule [-Werror=odr]
38 | class BOOST_SYMBOL_VISIBLE sp_counted_base
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:70:28: note: a different type is defined in another translation unit
70 | class BOOST_SYMBOL_VISIBLE sp_counted_base
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:45:26: note: the first difference of corresponding definitions is field ‘use_count_’
45 | boost::int_least32_t use_count_; // #shared
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:77:27: note: a field of same name but different type is defined in another translation unit
77 | boost::uint_least32_t use_count_; // #shared
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:38:28: note: type ‘int_least32_t’ should match type ‘uint_least32_t’
38 | class BOOST_SYMBOL_VISIBLE sp_counted_base
| ^
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:116:10: error: type of ‘release’ does not match original declaration [-Werror=lto-type-mismatch]
116 | void release() // nothrow
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:86:10: note: ‘release’ was previously declared here
86 | void release() noexcept
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:86:10: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:130:10: error: type of ‘weak_release’ does not match original declaration [-Werror=lto-type-mismatch]
130 | void weak_release() // nothrow
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:100:10: note: ‘weak_release’ was previously declared here
100 | void weak_release() noexcept
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:100:10: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
../../../boost/smart_ptr/detail/sp_counted_base_gcc_atomic.hpp:97:18: error: type of ‘destroy’ does not match original declaration [-Werror=lto-type-mismatch]
97 | virtual void destroy() // nothrow
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:65:18: note: ‘destroy’ was previously declared here
65 | virtual void destroy() noexcept // nothrow
| ^
../../../boost/smart_ptr/detail/sp_counted_base_nt.hpp:65:18: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
lto1: some warnings being treated as errors
lto-wrapper: fatal error: /usr/bin/x86_64-pc-linux-gnu-g++ returned 1 exit status
compilation terminated.
/usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../x86_64-pc-linux-gnu/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
...skipped abi_test_nt_mt.run for lack of abi_test_nt_mt...
common.mkdir ../../../bin.v2/libs/smart_ptr/test/get_deleter_test2_no_rtti.test/gcc-14.3

mkdir -p "../../../bin.v2/libs/smart_ptr/test/get_deleter_test2_no_rtti.test/gcc-14.3"
```

Originally reported downstream: https://bugs.gentoo.org/956660
Full build log: [build.log](https://github.com/user-attachments/files/24019656/build.log)