configure script: fix recursive mutex test on Linux systems (thanks, Ozkan!).

configure

@@ -21916,6 +21916,7 @@ $as_echo_n "checking for recursive mutexes... " >&6; }
                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+                  #define _GNU_SOURCE 1
                   #include <pthread.h>
 
 int
@@ -21929,7 +21930,7 @@ main ()
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
+if ac_fn_c_try_link "$LINENO"; then :
 
                 has_recursive_mutexes=yes
 
@@ -21937,12 +21938,14 @@ $as_echo "#define SDL_THREAD_PTHREAD_RECURSIVE_MUTEX 1" >>confdefs.h
 
 
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
             fi
             if test x$has_recursive_mutexes = xno; then
                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+                  #define _GNU_SOURCE 1
                   #include <pthread.h>
 
 int
@@ -21956,7 +21959,7 @@ main ()
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
+if ac_fn_c_try_link "$LINENO"; then :
 
                 has_recursive_mutexes=yes
 
@@ -21964,7 +21967,8 @@ $as_echo "#define SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP 1" >>confdefs.h
 
 
 fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
             fi
             { $as_echo "$as_me:${as_lineno-$LINENO}: result: $has_recursive_mutexes" >&5
 $as_echo "$has_recursive_mutexes" >&6; }

configure.in

@@ -2424,7 +2424,8 @@ AC_HELP_STRING([--enable-pthread-sem], [use pthread semaphores [[default=yes]]])
             AC_MSG_CHECKING(for recursive mutexes)
             has_recursive_mutexes=no
             if test x$has_recursive_mutexes = xno; then
-                AC_TRY_COMPILE([
+                AC_TRY_LINK([
+                  #define _GNU_SOURCE 1
                   #include <pthread.h>
                 ],[
                   pthread_mutexattr_t attr;
@@ -2435,7 +2436,8 @@ AC_HELP_STRING([--enable-pthread-sem], [use pthread semaphores [[default=yes]]])
                 ])
             fi
             if test x$has_recursive_mutexes = xno; then
-                AC_TRY_COMPILE([
+                AC_TRY_LINK([
+                  #define _GNU_SOURCE 1
                   #include <pthread.h>
                 ],[
                   pthread_mutexattr_t attr;