port binary dumping core on recent head in poudriere

Hi,

I've noticed that recently some ports are dumping core during builds of 
dependencies in head in poudriere.

I'm seeing this for example with sassc crashing while trying to build 
x11-themes/greybird-theme.

My first suspect was the llvm upgrade in head, but forcing sassc and 
libsass to build with older clang via USES=llvm:max=18 is not helping.

I did recompile the offending programs with debug and tried a backtrace 
and got this:

```
(lldb) bt
* thread #1, name = 'sassc', stop reason = signal SIGSEGV: invalid 
permissions for mapped object (fault address: 0x82374a000)
   * frame #0: 0x000000082374a000 libsass.so.1
     frame #1: 0x0000000823865a86 libsass.so.1`_GLOBAL__sub_I_ast.cpp 
[inlined] double std::__1::__math::acos[abi:se190102]<int, 0>(__x=-1) at 
inverse_trigonometric_functions.h:40:10
     frame #2: 0x0000000823865a81 libsass.so.1`_GLOBAL__sub_I_ast.cpp 
[inlined] __cxx_global_var_init at units.hpp:11:21
     frame #3: 0x0000000823865a81 libsass.so.1`_GLOBAL__sub_I_ast.cpp at 
ast.cpp:0
     frame #4: 0x00001eac6e3f078d ld-elf.so.1
     frame #5: 0x00001eac6e3ef349 ld-elf.so.1
     frame #6: 0x00001eac6e3ec099 ld-elf.so.1`___lldb_unnamed_symbol27 + 25
```

which points me to this upstream line of code: 
https://github.com/sass/libsass/blob/7037f03fabeb2b18b5efa84403f5a6d7a990f460/src/units.hpp#L11

I could change the way it derives PI, but I'm not sure this is the 
correct fix.


Thanks in advance for any insight!

-- 
Guido Falsi <mad@madpilot.net>