configure: Remove useless uses of ARCH_CFLAGS

Remove some useless uses of ARCH_CFLAGS -- this variable was never set
so will always be empty. The uses were accidental: in commit 0c439cbf8
Juan Quintela removed ARCH_CFLAGS in favour of CFLAGS (which in turn
became QEMU_CFLAGS). However in commit be17dc90 a use of it was
reintroduced (apparently accidentally) by Michael S. Tsirkin, and then
I subsequently cut-n-pasted that into a number of other configure
feature tests.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

configure

@@ -2369,7 +2369,7 @@ int main(void)
     return 0;
 }
 EOF
-if compile_prog "$ARCH_CFLAGS" "" ; then
+if compile_prog "" "" ; then
   fallocate=yes
 fi
 
@@ -2384,7 +2384,7 @@ int main(void)
     return 0;
 }
 EOF
-if compile_prog "$ARCH_CFLAGS" "" ; then
+if compile_prog "" "" ; then
   sync_file_range=yes
 fi
 
@@ -2401,7 +2401,7 @@ int main(void)
     return 0;
 }
 EOF
-if compile_prog "$ARCH_CFLAGS" "" ; then
+if compile_prog "" "" ; then
   fiemap=yes
 fi
 
@@ -2431,7 +2431,7 @@ int main(void)
     return 0;
 }
 EOF
-if compile_prog "$ARCH_CFLAGS" "" ; then
+if compile_prog "" "" ; then
   epoll=yes
 fi
 
@@ -2454,7 +2454,7 @@ int main(void)
     return epoll_create1 == epoll_create1;
 }
 EOF
-if compile_prog "$ARCH_CFLAGS" "" ; then
+if compile_prog "" "" ; then
   epoll_create1=yes
 fi
 
@@ -2468,7 +2468,7 @@ int main(void)
     return 0;
 }
 EOF
-if compile_prog "$ARCH_CFLAGS" "" ; then
+if compile_prog "" "" ; then
   epoll_pwait=yes
 fi