MUSL support

[repi]

Would be nice to be able to support building for and running on x86_64-unknown-linux-musl to use PhysX more easily across linux distributions.

Did a quick test compile and ran into this linking error:

  = note: /usr/bin/ld: /workspaces/ark/target/x86_64-unknown-linux-musl/release/deps/libphysx_sys-6a6d040663f16ba9.rlib(PsUnixFPU.o): undefined reference to symbol 'feenableexcept@@GLIBC_2.2.5'

looks like the fenv.h that physx is using in physx-sys/PhysX/physx/source/foundation/src/unix/PsUnixFPU.cpp uses a couple of GCC-specific extensions to the POSIX fenv.h that does not exist on MUSL:

PX_FOUNDATION_API void physx::shdfnd::enableFPExceptions()
{
#if PX_LINUX && !defined(__EMSCRIPTEN__)
	feclearexcept(FE_ALL_EXCEPT);
	feenableexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW);
#elif PX_OSX

Should be able to disable those fp exception functions similar to how it is disabled on Emscripten, but requires further patching the PhysX code. Don't think MUSL has a global preprocessor define enabled (or does it?) but we could provide one when building for x86_64-unknown-linux-musl target in build.rs

cc @Jake-Shadle

[repi]

Commenting out the FP exception functions and running our small ball_physx example results in a crash so more work would be need to investigate that.

(lldb) thread backtrace
error: need to add support for DW_TAG_base_type '()' encoded with DW_ATE = 0x7, bit_size = 0
error: need to add support for DW_TAG_base_type '()' encoded with DW_ATE = 0x7, bit_size = 0
* thread #1, name = 'ball_physx', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
  * frame #0: 0x0000000000000000
    frame #1: 0x00007ffff799e81f ball_physx`create_simulation_event_callbacks + 15
    frame #2: 0x00007ffff79994e2 ball_physx`physx::simulation_event_callback::PxSimulationEventCallback$LT$L$C$S$C$D$C$OC$C$OT$C$OCB$C$OWS$C$OA$GT$::new::h4637e7f3d90d3ca9(on_collide=None, on_trigger=None, on_constraint_break=None, on_wake_sleep=None, on_advance=Some) at simulation_event_callback.rs:99:17
    frame #3: 0x00007ffff79860c0 ball_physx`_$LT$physx..traits..descriptor..SceneDescriptor$LT$U$C$L$C$S$C$D$C$T$C$C$C$OC$C$OT$C$OCB$C$OWS$C$OA$GT$$u20$as$u20$physx..traits..descriptor..Descriptor$LT$P$GT$$GT$::create::hb169d9199454bdec(self=SceneDescriptor<(), physx::articulation_link::PxArticulationLink<(), physx::shape::PxShape<(), physx::material::PxMaterial<()>>>, physx::rigid_static::PxRigidStatic<(), physx::shape::PxShape<(), physx::material::PxMaterial<()>>>, physx::rigid_dynamic::PxRigidDynamic<(), physx::shape::PxShape<(), physx::material::PxMaterial<()>>>, physx::articulation::PxArticulation<(), physx::articulation_link::PxArticulationLink<(), physx::shape::PxShape<(), physx::material::PxMaterial<()>>>>, physx::articulation_reduced_coordinate::PxArticulationReducedCoordinate<(), physx::articulation_link::PxArticulationLink<(), physx::shape::PxShape<(), physx::material::PxMaterial<()>>>>, ball_physx::OnCollision, ball_physx::OnTrigger, ball_physx::OnConstraintBreak, ball_physx::OnWakeSleep, ball_physx::OnAdvance> @ 0x00007fffffffbe58, creator=0x00007fffffffc028) at descriptor.rs:209:42
    frame #4: 0x00007ffff7987962 ball_physx`physx::physics::Physics::create::h5439a1448557181d(self=0x00007fffffffc028, desc=<unavailable>) at physics.rs:246:9
    frame #5: 0x00007ffff7997a50 ball_physx`ball_physx::main::hf867c05f1057308f at ball_physx.rs:87:37
    frame #6: 0x00007ffff7983e4b ball_physx`core::ops::function::FnOnce::call_once::h4c21a1faa1ee8321((null)=(ball_physx`ball_physx::main::hf867c05f1057308f at ball_physx.rs:79), (null)=<unavailable>) at function.rs:227:5
    frame #7: 0x00007ffff798b47e ball_physx`std::sys_common::backtrace::__rust_begin_short_backtrace::h2f749092f39794ea(f=(ball_physx`ball_physx::main::hf867c05f1057308f at ball_physx.rs:79)) at backtrace.rs:125:18
    frame #8: 0x00007ffff7988c01 ball_physx`std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::h064f6c6770b34b01 at rt.rs:63:18
    frame #9: 0x00007ffff7e4b760 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b [inlined] core::ops::function::impls::_$LT$impl$u20$core..ops..function..FnOnce$LT$A$GT$$u20$for$u20$$RF$F$GT$::call_once::h5edb75ac3af12064 at function.rs:259:13
    frame #10: 0x00007ffff7e4b755 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b [inlined] std::panicking::try::do_call::h4398f4e6da05592f at panicking.rs:401
    frame #11: 0x00007ffff7e4b755 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b [inlined] std::panicking::try::h3fe03463ab3f9a9d at panicking.rs:365
    frame #12: 0x00007ffff7e4b755 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b [inlined] std::panic::catch_unwind::h3f31a496b3e5f0e5 at panic.rs:434
    frame #13: 0x00007ffff7e4b755 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b [inlined] std::rt::lang_start_internal::_$u7b$$u7b$closure$u7d$$u7d$::h24e3f631c8bb6bd5 at rt.rs:45
    frame #14: 0x00007ffff7e4b755 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b [inlined] std::panicking::try::do_call::h9268f45ee0925288 at panicking.rs:401
    frame #15: 0x00007ffff7e4b755 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b [inlined] std::panicking::try::he93fcdbaacc3daf7 at panicking.rs:365
    frame #16: 0x00007ffff7e4b755 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b [inlined] std::panic::catch_unwind::hca9f2323bf3773b4 at panic.rs:434
    frame #17: 0x00007ffff7e4b755 ball_physx`std::rt::lang_start_internal::hfee0032b3594c35b at rt.rs:45
    frame #18: 0x00007ffff7988bd0 ball_physx`std::rt::lang_start::hbcaa456adb732f31(main=(ball_physx`ball_physx::main::hf867c05f1057308f at ball_physx.rs:79), argc=1, argv=0x00007fffffffc5c8) at rt.rs:62:5
    frame #19: 0x00007ffff799806c ball_physx`main + 28
    frame #20: 0x00007ffff7e6efe8 ball_physx`libc_start_main_stage2 + 39
    frame #21: 0x00007ffff7982801 ball_physx`_start + 22

[Jake-Shadle]

No, musl does not have any default preprocessor definitions for detection, so yes the easiest would just be to add a musl preprocessor definition if targeting it.