Arch Linux

Description:
Any program compiled with clang -Ofast ( or -O2 -ffast-math ) that uses exp/pow/log etc functions, fails to link now.

Additional info:
* Using extra/clang 9.0.1-1 and core/glibc 2.31-1

Steps to reproduce:

1. Create the folowing file as 'test.cpp'
```
#include <cstdio>
int main(int argc,char **argv)
{
printf("%f\n",__builtin_expf(float(argv[1][0])));
return 0;
}
```
2. try to compile with `clang++ -Ofast z.cpp -lm`
3. error occurs:
/usr/bin/ld: /tmp/test-a8aed5.o: in function `main':
test.cpp:(.text+0xd): undefined reference to `__expf_finite'
clang-9: error: linker command failed with exit code 1 (use -v to see invocation)

Note: in libm the `__expf_finite` exists as indirect function.
00000000000437c0 i __expf_finite