ln is not available on all platforms, so introduce a variable for it

that can be set to a suitable platform-specific command.
patch by Dave Yeo, daveryeo telus net

Originally committed as revision 10503 to svn://svn.ffmpeg.org/ffmpeg/trunk

common.mak

@@ -27,7 +27,7 @@ $(LIB): $(STATIC_OBJS)
 	$(RANLIB) $@
 
 $(SLIBNAME): $(SLIBNAME_WITH_MAJOR)
-	ln -sf $^ $@
+	$(LN_S) $^ $@
 
 $(SLIBNAME_WITH_MAJOR): $(SHARED_OBJS)
 	$(CC) $(SHFLAGS) $(LDFLAGS) -o $@ $^ $(EXTRALIBS) $(EXTRAOBJS)
@@ -74,9 +74,9 @@ install-lib-shared: $(SLIBNAME)
 	install -m 755 $(SLIBNAME) "$(SHLIBDIR)/$(SLIBNAME_WITH_VERSION)"
 	$(STRIP) "$(SHLIBDIR)/$(SLIBNAME_WITH_VERSION)"
 	cd "$(SHLIBDIR)" && \
-		ln -sf $(SLIBNAME_WITH_VERSION) $(SLIBNAME_WITH_MAJOR)
+		$(LN_S) $(SLIBNAME_WITH_VERSION) $(SLIBNAME_WITH_MAJOR)
 	cd "$(SHLIBDIR)" && \
-		ln -sf $(SLIBNAME_WITH_VERSION) $(SLIBNAME)
+		$(LN_S) $(SLIBNAME_WITH_VERSION) $(SLIBNAME)
 	$(SLIB_INSTALL_EXTRA_CMD)
 
 install-lib-static: $(LIB)

configure

@@ -835,6 +835,7 @@ ranlib="ranlib"
 make="make"
 strip="strip"
 asmalign_pot="unknown"
+ln_s="ln -sf"
 
 # machine
 arch=`uname -m`
@@ -1219,6 +1220,7 @@ cc="${cross_prefix}${cc}"
 ar="${cross_prefix}${ar}"
 ranlib="${cross_prefix}${ranlib}"
 strip="${cross_prefix}${strip}"
+ln_s="${cross_prefix}${ln_s}"
 
 # we need to build at least one lib type
 if ! enabled_any static shared; then
@@ -1879,6 +1881,7 @@ echo "MAKE=$make" >> config.mak
 echo "CC=$cc" >> config.mak
 echo "AR=$ar" >> config.mak
 echo "RANLIB=$ranlib" >> config.mak
+echo "LN_S=$ln_s" >> config.mak
 if enabled dostrip; then
     echo "STRIP=$strip" >> config.mak
 else
@@ -2022,7 +2025,7 @@ if enabled source_path_used; then
             mkdir -p $dir
     done
     for f in $FILES ; do
-        ln -sf "$source_path/$f" $f
+        $ln_s "$source_path/$f" $f
     done
 fi