[libunwind] [test] Mark the signal_frame test as unsupported on Windows

[mstorsjo]

Summary

Mark it as unsupported on x86_64, arm and aarch64. On i686, DWARF
is used as the default unwinding format, and there, the CFI
directives are supported.

I'm not sure if it's worth to keep the complex regex to allow the
test to be run on i686 - we could also just mark it unsupported on
all windows variants.

[phosek]

LGTM

libunwind/test/signal_frame.pass.cpp

 // XFAIL: msan
 
 // UNSUPPORTED: libunwind-arm-ehabi
 
 // The AIX assembler does not support CFI directives, which
 // are necessary to run this test.
 // UNSUPPORTED: target=powerpc{{(64)?}}-ibm-aix
 
+// Windows doesn't generally use CFI directives. However, i686
+// mingw targets do use DWARF (where CFI directives are supported).
+// UNSUPPORTED: target={{x86_64|arm.*|aarch64}}-{{.*}}-windows-{{.*}}
+
 #undef NDEBUG
 #include <assert.h>
 #include <stdlib.h>
 #include <libunwind.h>
 
 void test() {
   asm(".cfi_signal_frame");
   unw_cursor_t cursor;