Link error when using `getrandom`

When trying to use `getrandom` from MUSL's [``](https://github.com/emscripten-core/emscripten/blob/e00597b511c16aa40da0c36f7c773b96e3f246af/system/lib/libc/musl/include/sys/random.h#L15), it fails to link with "undefined symbol: getrandom".

Note that `getentropy` works fine, as it seems to [be defined](https://github.com/emscripten-core/emscripten/blob/3775844052a64bedde2de12ad2ee849ea6160c11/system/lib/libc/musl/src/misc/getentropy.c#L22) in terms of `__wasi_random_get` for `__EMSCRIPTEN__`.

I'm not sure if `getrandom` is actually implemented? It just [implemented](https://github.com/emscripten-core/emscripten/blob/e00597b511c16aa40da0c36f7c773b96e3f246af/system/lib/libc/musl/src/linux/getrandom.c) as `syscall_cp(SYS_getrandom, ...)` at the moment. But then why is the header present?

**Version of emscripten/emsdk:**

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 6.0.2 (7a2d97d627ff4945eae28847ce0387ac52b92c09)

**Failing command line in full:**

`getrandom.cpp`
```c++
#include
#include
#include
#include
#include

int main() {
std::array buf;
if (::getrandom(buf.data(), buf.size(), 0) < 0) {
::perror("random failed");
}
for (unsigned char c : buf) {
std::cout << unsigned{c} << ' ';
}
std::cout << std::endl;
}
```

```
$ em++ getrandom.cpp -o getrandom -v
"/home/swdv/emsdk/upstream/bin/clang++" -target wasm32-unknown-emscripten -fignore-exceptions -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --sysroot=/home/swdv/emsdk/upstream/emscripten/cache/sysroot -Xclang -iwithsysroot/include/fakesdl -Xclang -iwithsysroot/include/compat -v -c getrandom.cpp -o /tmp/emscripten_temp_jack687l/getrandom.o
clang version 23.0.0git (https:/github.com/llvm/llvm-project 787619a4072e0eb7887357d5d284e86c17548aed)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /home/swdv/emsdk/upstream/bin
(in-process)
"/home/swdv/emsdk/upstream/bin/clang-23" -cc1 -triple wasm32-unknown-emscripten -emit-obj -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name getrandom.cpp -mrelocation-model static -mframe-pointer=none -ffp-contract=on -fno-rounding-math -mconstructor-aliases -target-cpu generic -fvisibility=hidden -debugger-tuning=gdb -fdebug-compilation-dir=/home/swdv -v -fcoverage-compilation-dir=/home/swdv -resource-dir /home/swdv/emsdk/upstream/lib/clang/23 -isysroot /home/swdv/emsdk/upstream/emscripten/cache/sysroot -internal-isystem /home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten/noeh/c++/v1 -internal-isystem /home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten/c++/v1 -internal-isystem /home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1 -internal-isystem /home/swdv/emsdk/upstream/lib/clang/23/include -internal-isystem /home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten -internal-isystem /home/swdv/emsdk/upstream/emscripten/cache/sysroot/include -fdeprecated-macro -ferror-limit 19 -fmessage-length=214 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcxx-exceptions -fignore-exceptions -fexceptions -fcolor-diagnostics -iwithsysroot/include/fakesdl -iwithsysroot/include/compat -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -o /tmp/emscripten_temp_jack687l/getrandom.o -x c++ getrandom.cpp
clang -cc1 version 23.0.0git based upon LLVM 23.0.0git default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten/noeh/c++/v1"
ignoring nonexistent directory "/home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten/c++/v1"
ignoring nonexistent directory "/home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten"
#include "..." search starts here:
#include <...> search starts here:
/home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/fakesdl
/home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/compat
/home/swdv/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1
/home/swdv/emsdk/upstream/lib/clang/23/include
/home/swdv/emsdk/upstream/emscripten/cache/sysroot/include
End of search list.
/home/swdv/emsdk/upstream/bin/clang --version
/home/swdv/emsdk/upstream/bin/wasm-ld -o getrandom.wasm /tmp/tmprijrpay7libemscripten_js_symbols.so -Bstatic --strip-debug --export=emscripten_stack_get_end --export=emscripten_stack_get_free --export=emscripten_stack_get_base --export=emscripten_stack_get_current --export=emscripten_stack_init --export=_emscripten_stack_alloc --export=__wasm_call_ctors --export=_emscripten_stack_restore --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-if-defined=__start_em_lib_deps --export-if-defined=__stop_em_lib_deps --export-if-defined=__start_em_js --export-if-defined=__stop_em_js --export-if-defined=main --export-if-defined=__main_argc_argv --export-if-defined=fflush --export-table -z stack-size=65536 --no-growable-memory --initial-heap=16777216 --no-entry --stack-first --table-base=1 /tmp/emscripten_temp_jack687l/getrandom.o -L/home/swdv/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -L/home/swdv/emsdk/upstream/emscripten/src/lib -lGL-getprocaddr -lal -lhtml5 -lstubs-debug -lnoexit -lc-debug -ldlmalloc-debug -lclang_rt.builtins -lc++-debug-noexcept -lc++abi-debug-noexcept -lsockets -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr
wasm-ld: error: /tmp/emscripten_temp_jack687l/getrandom.o: undefined symbol: getrandom
em++: error: '/home/swdv/emsdk/upstream/bin/wasm-ld -o getrandom.wasm /tmp/tmprijrpay7libemscripten_js_symbols.so -Bstatic --strip-debug --export=emscripten_stack_get_end --export=emscripten_stack_get_free --export=emscripten_stack_get_base --export=emscripten_stack_get_current --export=emscripten_stack_init --export=_emscripten_stack_alloc --export=__wasm_call_ctors --export=_emscripten_stack_restore --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-if-defined=__start_em_lib_deps --export-if-defined=__stop_em_lib_deps --export-if-defined=__start_em_js --export-if-defined=__stop_em_js --export-if-defined=main --export-if-defined=__main_argc_argv --export-if-defined=fflush --export-table -z stack-size=65536 --no-growable-memory --initial-heap=16777216 --no-entry --stack-first --table-base=1 /tmp/emscripten_temp_jack687l/getrandom.o -L/home/swdv/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -L/home/swdv/emsdk/upstream/emscripten/src/lib -lGL-getprocaddr -lal -lhtml5 -lstubs-debug -lnoexit -lc-debug -ldlmalloc-debug -lclang_rt.builtins -lc++-debug-noexcept -lc++abi-debug-noexcept -lsockets -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr' failed (returned 1)
```

Start by running the supplied em++ command and comparing sys/random.h with musl/src/linux/getrandom.c and musl/src/misc/getentropy.c. Trace how the existing getentropy implementation is linked for __EMSCRIPTEN__, then verify that the getrandom example links without an undefined symbol and preserves the expected random-data behavior.

Written by the indexing model from the issue text.