Remove execinfo.h include in WinAdapter.h (#3797)

This small change makes it possible to build and use
DirectXShaderCompiler on Android, at least on arm64-v8a.

execinfo.h does not exist in Android toolchain. However it is
only used by clang-hlsl-tests which can be disabled from the build.

CaptureStackBackTrace is not used in any files
compiled in non-Windows builds. This is because CompilerTest.cpp,
where it was used, is disabled from non-Windows build at the moment.

Co-authored-by: Atte Seppälä <[email protected]>

Author: seppala2

include/dxc/Support/WinAdapter.h

@@ -32,7 +32,6 @@
 #include <typeinfo>
 #include <vector>
 #endif // __cplusplus
-#include <execinfo.h>
 
 //===----------------------------------------------------------------------===//
 //
@@ -195,10 +194,6 @@
 #define OutputDebugStringA(msg) fputs(msg, stderr)
 #define OutputDebugFormatA(...) fprintf(stderr, __VA_ARGS__)
 
-#define CaptureStackBackTrace(FramesToSkip, FramesToCapture, BackTrace,        \
-                              BackTraceHash)                                   \
-  backtrace(BackTrace, FramesToCapture)
-
 // Event Tracing for Windows (ETW) provides application programmers the ability
 // to start and stop event tracing sessions, instrument an application to
 // provide trace events, and consume trace events.