[wpiutil] Avoid including execinfo.h for Emscripten target (#7854)

wpiutil/src/main/native/unix/StackTrace.cpp

@@ -4,7 +4,9 @@
 
 #include "wpi/StackTrace.h"
 
+#ifndef __EMSCRIPTEN__
 #include <execinfo.h>
+#endif
 
 #include <string>
 
@@ -16,7 +18,7 @@
 namespace wpi {
 
 std::string GetStackTraceDefault(int offset) {
-#ifndef __ANDROID__
+#if !defined(__ANDROID__) && !defined(__EMSCRIPTEN__)
   void* stackTrace[128];
   int stackSize = backtrace(stackTrace, 128);
   char** mangledSymbols = backtrace_symbols(stackTrace, stackSize);
@@ -40,7 +42,7 @@ std::string GetStackTraceDefault(int offset) {
 
   return std::string{trace.str()};
 #else
-  // backtrace_symbols not supported on android
+  // backtrace_symbols not supported
   return "";
 #endif
 }