gcc4: build with --with-gnu-ld

This allows gcc to pass response files directly to LD, allowing to build
WebKit libraries using them without hitting command-line length limit.

Also REQUIRES binutils at the proper version, as using binutils 2.17 with
gcc4 isn't working (as doesn't understand some directives).

sys-devel/gcc/gcc-4.7.3_2013_08_12.recipe

@@ -10,7 +10,7 @@ SRC_URI="
 	git+file://$portBaseDir/../binutils/download/BuildtoolsPM.git#2d0a2c6404ffae1a46eb7e74daab08099b45af2c
 	git+git://github.com/haiku/BuildtoolsPM.git#2d0a2c6404ffae1a46eb7e74daab08099b45af2c
 	"
-REVISION="2"
+REVISION="3"
 ARCHITECTURES="x86 x86_64"
 if [ $effectiveTargetArchitecture != x86_gcc2 ]; then
 	# x86_gcc2 is fine as primary target architecture as long as we're building
@@ -32,6 +32,7 @@ PROVIDES="
 
 REQUIRES="
 	haiku$secondaryArchSuffix >= $haikuVersion
+	cmd:as$secondaryArchSuffix
 	"
 BUILD_REQUIRES="
 	"
@@ -83,7 +84,7 @@ BUILD()
 		--build=$effectiveTargetMachineTriple \
 		--prefix=$installDir --libexecdir=$installDir/lib --mandir=$manDir \
 		--docdir=$docDir \
-		--disable-nls --enable-shared \
+		--disable-nls --enable-shared --with-gnu-ld \
 		--enable-languages=c,c++ --enable-lto --enable-frame-pointer \
 		--with-pkgversion=$(echo $portVersion | cut -c 7-) \
 		$additionalConfigureFlags