cmd/cgo, cmd/cc, cmd/ld: detect dynamic linker automatically

Some newer Linux distributions (Ubuntu ARM at least) use a new multiarch
directory organization, where dynamic linker is no longer in the hardcoded
path in our linker.
For example, Ubuntu 12.04 ARM hardfloat places its dynamic linker at
/lib/arm-linux-gnueabihf/ld-linux.so.3

Ref: http://lackof.org/taggart/hacking/multiarch/

Also, to support Debian GNU/kFreeBSD as a FreeBSD variant, we need this capability, so it's part of issue 3533.

This CL add a new pragma (#pragma dynlinker "path") to cc.

R=iant, rsc
CC=golang-dev
http://codereview.appspot.com/6086043

1 files changed, 4 insertions, 0 deletions

diff --git a/src/cmd/cc/macbody b/src/cmd/cc/macbody
index 874e82d25..e9b4ba9fb 100644
--- a/src/cmd/cc/macbody
+++ b/src/cmd/cc/macbody
@@ -751,6 +751,10 @@ macprag(void)
 		pragdynexport();
 		return;
 	}
+	if(s && strcmp(s->name, "dynlinker") == 0) {
+		pragdynlinker();
+		return;
+	}
 	while(getnsc() != '\n')
 		;
 	return;