[libc++abi] Disable forced_unwind4 test for musl. (#85096)

This test won't pass on musl, but we should still run it for other Linux
platforms.

rdar://123436716

Author: al45tair

libcxxabi/test/forced_unwind4.pass.cpp

@@ -7,10 +7,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-// REQUIRES: linux && target={{aarch64-.+}}
+// REQUIRES: linux && target=aarch64-{{.+}}-gnu
 
 // pthread_cancel in case of glibc calls _Unwind_ForcedUnwind from a signal on
-// the child_thread. This test ensures sigretrun is handled correctly (see:
+// the child_thread. This test ensures sigreturn is handled correctly (see:
 // UnwindCursor<A, R>::setInfoForSigReturn).
 
 #include <cstdlib> // defines __BIONIC__