Test fails for LLVM8 / llvmlite 0.29 / ROC 2.4.0

We had a [patch](https://aur.archlinux.org/cgit/aur.git/tree/link_dynamic_fix_triplet.patch?h=python-numba-roctools-git) for Arch Linux keeping roctools alive for LLVM7.0.0/ROC2.2.0. With LLVM8.0.0/llvmlite0.29/ROC2.4.0 test_rocmlite_functions crashes as follows:

```
Running main() from /build/gtest/src/googletest-release-1.8.1/googletest/src/gtest_main.cc
[==========] Running 8 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 8 tests from C_Linkage_Functions
[ RUN ] C_Linkage_Functions.String_Manipulation
[ OK ] C_Linkage_Functions.String_Manipulation (0 ms)
[ RUN ] C_Linkage_Functions.test_parse_ir_module
[ OK ] C_Linkage_Functions.test_parse_ir_module (1 ms)
[ RUN ] C_Linkage_Functions.test_parse_bc_module
Unknown attribute kind (60) (Producer: 'LLVM4.0.0' Reader: 'LLVM 8.0.0')
#0 0x00007f61fa34afdb llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/usr/lib/libLLVM-8.so+0x9f5fdb)
#1 0x00007f61fa348e84 llvm::sys::RunSignalHandlers() (/usr/lib/libLLVM-8.so+0x9f3e84)
#2 0x00007f61fa34900e (/usr/lib/libLLVM-8.so+0x9f400e)
#3 0x00007f61f961b8b0 __restore_rt (/usr/lib/libc.so.6+0x378b0)
#4 0x00007f61fdf3db39 librocmlite::ModuleRef::destroy() /home/maverick/builds/python-numba-roctools-git/src/roctools/rocmlite/rocmlite.cpp:96:16
#5 0x00007f61fdf3e299 ROC_ModuleDestroy /home/maverick/builds/python-numba-roctools-git/src/roctools/rocmlite/rocmlite.cpp:633:9
#6 0x000055d6e22fdf5e (librocmlite+0x11f5e)
#7 0x00007f61fde7388b void testing::internal::HandleExceptionsInMethodIfSupported(testing::Test*, void (testing::Test::*)(), char const*) (/usr/lib/libgtest.so.1.8.1+0x4388b)
#8 0x00007f61fde69b2c testing::Test::Run() (/usr/lib/libgtest.so.1.8.1+0x39b2c)
#9 0x00007f61fde69c89 testing::TestInfo::Run() (/usr/lib/libgtest.so.1.8.1+0x39c89)
#10 0x00007f61fde69d67 testing::TestCase::Run() (/usr/lib/libgtest.so.1.8.1+0x39d67)
#11 0x00007f61fde6a29d testing::internal::UnitTestImpl::RunAllTests() (/usr/lib/libgtest.so.1.8.1+0x3a29d)
#12 0x00007f61fde73dfb bool testing::internal::HandleExceptionsInMethodIfSupported(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) (/usr/lib/libgtest.so.1.8.1+0x43dfb)
#13 0x00007f61fde6a3cf testing::UnitTest::Run() (/usr/lib/libgtest.so.1.8.1+0x3a3cf)
#14 0x00007f61fde2c05f main (/usr/lib/libgtest_main.so.1.8.1+0x105f)
#15 0x00007f61f9607ce3 __libc_start_main (/usr/lib/libc.so.6+0x23ce3)
#16 0x000055d6e22fc89e (librocmlite+0x1089e)
[1] 15660 segmentation fault (core dumped) ./test_rocmlite_functions
```