Port Unix/ossource.cpp to Fuchsia

Fuchsia has pthreads but doesn't have sys/resource.h and doesn't
implement pthread_cleanup_push().

ANGLE bug: 2475

glslang/OSDependent/Unix/ossource.cpp

@@ -45,7 +45,10 @@
 #include <stdint.h>
 #include <cstdio>
 #include <sys/time.h>
+
+#if !defined(__Fuchsia__)
 #include <sys/resource.h>
+#endif
 
 namespace glslang {
 
@@ -70,7 +73,7 @@ static void DetachThreadLinux(void *)
 //
 void OS_CleanupThreadData(void)
 {
-#ifdef __ANDROID__
+#if defined(__ANDROID__) || defined(__Fuchsia__)
     DetachThreadLinux(NULL);
 #else
     int old_cancel_state, old_cancel_type;