[gobject-introspection] configure: Don't declare functions in AC_TRY_COMPILE and AC_LANG_PROGRAM

[Ting-Wei Lan <lantw src gnome org>]

commit cafe43fa9def848bb5c974aab818d7dd7ed1f0d7
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Sat Jan 20 17:16:48 2018 +0800

    configure: Don't declare functions in AC_TRY_COMPILE and AC_LANG_PROGRAM
    
    https://bugzilla.gnome.org/show_bug.cgi?id=792714

 configure.ac |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 283a2e5..a6e7b36 100644
--- a/configure.ac
+++ b/configure.ac
@@ -322,7 +322,7 @@ case "$host" in
     SAVED_CFLAGS="${CFLAGS}"
     CFLAGS="-fvisibility=hidden"
     AC_MSG_CHECKING([for -fvisibility=hidden compiler flag])
-    AC_TRY_COMPILE([], [int main (void) { return 0; }],
+    AC_TRY_COMPILE([], [return 0],
                    AC_MSG_RESULT(yes)
                    enable_fvisibility_hidden=yes,
                    AC_MSG_RESULT(no)
@@ -348,7 +348,7 @@ AC_ARG_ENABLE(Bsymbolic,
               [SAVED_LDFLAGS="${LDFLAGS}"
                AC_MSG_CHECKING([for -Bsymbolic-functions linker flag])
                LDFLAGS=-Wl,-Bsymbolic-functions
-               AC_LINK_IFELSE([AC_LANG_PROGRAM([[]], [[int main (void) { return 0; }]])],
+               AC_LINK_IFELSE([AC_LANG_PROGRAM([[]], [[return 0]])],
                               [AC_MSG_RESULT(yes)
                                enable_Bsymbolic=yes],
                               [AC_MSG_RESULT(no)