Add rpath to host executables

Host executables need rpath set so they can find their shared
libraries.

Change-Id: I297682d3266bb436af0f594e8164ee4b9e7ab234

cc/x86_linux_host.go

@@ -61,10 +61,12 @@ var (
 
 	linuxX86Ldflags = []string{
 		"-m32",
+		`-Wl,-rpath,\$$ORIGIN/../lib`,
 	}
 
 	linuxX8664Ldflags = []string{
 		"-m64",
+		`-Wl,-rpath,\$$ORIGIN/../lib64`,
 	}
 
 	linuxClangCflags = append([]string{