build: Hide glibc workarounds in PLATFORM_LINUX because it does only make sense on Linux.

src/tvheadend.h

@@ -603,12 +603,14 @@ int rmtree ( const char *path );
 
 char *regexp_escape ( const char *str );
 
+#ifdef PLATFORM_LINUX
 /* glibc wrapper */
 #if !__GLIBC_PREREQ(2,8)
 void
 qsort_r(void *base, size_t nmemb, size_t size,
        int (*cmp)(const void *, const void *, void *), void *aux);
 #endif
+#endif /* PLATFORM_LINUX */
 
 /* printing */
 # if __WORDSIZE == 64

src/wrappers.c

@@ -123,6 +123,7 @@ tvhthread_create0
   return r;
 }
 
+#ifdef PLATFORM_LINUX
 /*
  * qsort_r wrapper for pre GLIBC 2.8
  */
@@ -148,3 +149,4 @@ qsort_r(void *base, size_t nmemb, size_t size,
   qsort(base, nmemb, size, qsort_r_wrap);
 }
 #endif /* GLIBC < 2.8 */
+#endif /* PLATFORM_LINUX */