Compile .S files with $(AS), set it in configure

Assembler files using the GNU syntax need to be processed by gcc,
whichever compiler is used for C files.

Originally committed as revision 17827 to svn://svn.ffmpeg.org/ffmpeg/trunk

common.mak

@@ -24,7 +24,7 @@ CFLAGS := -DHAVE_AV_CONFIG_H -I$(BUILD_ROOT_REL) -I$(SRC_PATH) $(OPTFLAGS)
 	$(CC) $(CFLAGS) $(LIBOBJFLAGS) -c -o $@ $<
 
 %.o: %.S
-	$(CC) $(CFLAGS) $(LIBOBJFLAGS) -c -o $@ $<
+	$(AS) $(CFLAGS) $(LIBOBJFLAGS) -c -o $@ $<
 
 %.ho: %.h
 	$(CC) $(CFLAGS) $(LIBOBJFLAGS) -Wno-unused -c -o $@ -x c $<

configure

@@ -178,6 +178,7 @@ show_help(){
   echo "  --target-exec=CMD        command to run executables on target"
   echo "  --target-path=DIR        path to view of build directory on target"
   echo "  --nm=NM                  use nm tool"
+  echo "  --as=AS                  use assembler AS [$as_default]"
   echo "  --cc=CC                  use C compiler CC [$cc_default]"
   echo "  --host-cc=HOSTCC         use host C compiler HOSTCC"
   echo "  --host-cflags=HCFLAGS    use HCFLAGS when compiling for host"
@@ -938,6 +939,7 @@ PATHS_LIST='
 CMDLINE_SET="
     $PATHS_LIST
     arch
+    as
     build_suffix
     cc
     cpu
@@ -1140,6 +1142,7 @@ shlibdir_default="$libdir_default"
 
 # toolchain
 ar="ar"
+as_default="gcc"
 cc_default="gcc"
 host_cc_default="gcc"
 ln_s="ln -sf"
@@ -1306,6 +1309,7 @@ set >> $logfile
 test -n "$cross_prefix" && enable cross_compile
 
 ar="${cross_prefix}${ar}"
+as_default="${cross_prefix}${as_default}"
 cc_default="${cross_prefix}${cc_default}"
 nm_default="${cross_prefix}${nm_default}"
 ranlib="${cross_prefix}${ranlib}"
@@ -1313,7 +1317,7 @@ strip="${cross_prefix}${strip}"
 
 sysinclude_default="${sysroot}/usr/include"
 
-set_default cc nm sysinclude
+set_default as cc nm sysinclude
 enabled cross_compile || host_cc_default=$cc
 set_default host_cc
 
@@ -2329,6 +2333,7 @@ echo "BINDIR=\$(DESTDIR)$bindir" >> config.mak
 echo "DATADIR=\$(DESTDIR)$datadir" >> config.mak
 echo "MANDIR=\$(DESTDIR)$mandir" >> config.mak
 echo "CC=$cc" >> config.mak
+echo "AS=$as" >> config.mak
 echo "YASM=$yasmexe" >> config.mak
 echo "AR=$ar" >> config.mak
 echo "RANLIB=$ranlib" >> config.mak