Prefer __GLIBC__ check over individual platforms in Stubs.cpp

Author: grynspan

Sources/_TestingInternals/Stubs.cpp

@@ -17,12 +17,10 @@
 /// include functions here if Swift cannot successfully import and call them
 /// otherwise.
 
-#if defined(__linux__) || defined(__FreeBSD__)
 #undef _DEFAULT_SOURCE
 #define _DEFAULT_SOURCE 1
 #undef _GNU_SOURCE
 #define _GNU_SOURCE 1
-#endif
 
 #include "Stubs.h"
 
@@ -32,7 +30,7 @@ int swt_pthread_setname_np(pthread_t thread, const char *name) {
 }
 #endif
 
-#if defined(__linux__) || defined(__FreeBSD__)
+#if defined(__GLIBC__)
 int swt_posix_spawn_file_actions_addclosefrom_np(posix_spawn_file_actions_t *fileActions, int from) {
   int result = 0;
 

Sources/_TestingInternals/include/Stubs.h

@@ -118,7 +118,7 @@ static char *_Nullable *_Null_unspecified swt_environ(void) {
 SWT_EXTERN int swt_pthread_setname_np(pthread_t thread, const char *name);
 #endif
 
-#if defined(__linux__) || defined(__FreeBSD__)
+#if defined(__GLIBC__)
 /// Close file descriptors above a given value when spawing a new process.
 ///
 /// This symbol is provided because the underlying function was added to glibc