[PATCH] Support cross compiling to arm on ubuntu.

[Logan Chien]

  Besides, I feel it will be even better to add the test cases for arm-linux-gnueabi as well.

  FYI.  I have created a patch for this change:
  https://github.com/loganchien/clang/compare/b0e00c2...630a9e3


================
Comment at: test/Driver/linux-ld.c:260
@@ +259,3 @@
+// CHECK-X86-64-UBUNTU-13-10-ARM-HF: "-L[[SYSROOT]]/usr/lib/gcc-cross/arm-linux-gnueabihf/4.8/../../../../arm-linux-gnueabihf/lib/../lib"
+// CHECK-X86-64-UBUNTU-13-10-ARM-HF: "-L[[SYSROOT]]/lib/../lib"
+// CHECK-X86-64-UBUNTU-13-10-ARM-HF: "-L[[SYSROOT]]/usr/lib/../lib"
----------------
It seems that SYSROOT/lib is not added to version control.  Maybe you have to put a placeholder such as .keep?

e.g.
mkdir -p Inputs/x86-64_ubuntu_13.10/lib
touch Inputs/x86-64_ubuntu_13.10/lib/.keep
git add Inputs/x86-64_ubuntu_13.10/lib/.keep

================
Comment at: test/Driver/linux-ld.c:262
@@ +261,3 @@
+// CHECK-X86-64-UBUNTU-13-10-ARM-HF: "-L[[SYSROOT]]/usr/lib/../lib"
+// CHECK-X86-64-UBUNTU-13-10-ARM-HF: "-L[[SYSROOT]]/usr/lib/gcc-cross/arm-linux-gnueabihf/4.8/../../../../arm-linux-gnueabihf/lib"
+// CHECK-X86-64-UBUNTU-13-10-ARM-HF: "{{.*}}/usr/lib/gcc-cross/arm-linux-gnueabihf/4.8/crtend.o"
----------------
It seems we can add two more checks after this line:
CHECK-X86-64-UBUNTU-13-10-ARM-HF: "-L[[SYSROOT]]/usr/lib/gcc-cross/arm-linux-gnueabihf/4.8/../../.."
CHECK-X86-64-UBUNTU-13-10-ARM-HF: "-L[[SYSROOT]]/usr/lib"


http://llvm-reviews.chandlerc.com/D2031