[test] Fix baremetal test to allow any -resource-dir

[mgorny]

Summary

The baremetal test (r303873) has been added with expectance of very
specific -resource-dir. However, the test itself nor the BareMetal
driver does not enforce any specific -resource-dir, making this
constraint invalid. It already has been altered twice -- in r303910 for
Windows compatibility, and in r304085 for systems using lib64. To
account for even more systems, just use [[RESOURCE_DIR]] like a number
of other tests do. This is needed for Gentoo where RESOURCE_DIR starts
with ../ (uses relative path to a parent directory).

[jroelofs]

LGTM... thank you!

cfe/trunk/test/Driver/baremetal.cpp

 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     -target armv6m-none-eabi \
 // RUN:     -T semihosted.lds \
 // RUN:     -L some/directory/user/asked/for \
 // RUN:     --sysroot=%S/Inputs/baremetal_arm \
 // RUN:   | FileCheck --check-prefix=CHECK-V6M-C %s
 // CHECK-V6M-C: "[[PREFIX_DIR:.*]]{{[/\\]+}}{{[^/^\\]+}}{{[/\\]+}}clang{{.*}}" "-cc1" "-triple" "thumbv6m-none--eabi"
-// CHECK-V6M-C-SAME: "-resource-dir" "[[PREFIX_DIR]]{{[/\\]+}}lib{{(64)?}}{{[/\\]+}}clang{{[/\\]+}}[[VERSION:[^"]*]]"
+// CHECK-V6M-C-SAME: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // CHECK-V6M-C-SAME: "-isysroot" "[[SYSROOT:[^"]*]]"
 // CHECK-V6M-C-SAME: "-internal-isystem" "[[SYSROOT]]{{[/\\]+}}include{{[/\\]+}}c++{{[/\\]+}}v1"
 // CHECk-V6M-C-SAME: "-internal-isystem" "[[SYSROOT]]{{[/\\]+}}include"
 // CHECK-V6M-C-SAME: "-x" "c++" "{{.*}}baremetal.cpp"
 // CHECK-V6M-C-NEXT: "{{[^"]*}}ld.lld" "{{.*}}.o" "-Bstatic"
-// CHECK-V6M-C-SAME: "-L[[PREFIX_DIR]]{{[/\\]+}}lib{{(64)?}}{{[/\\]+}}clang{{[/\\]+}}[[VERSION]]{{[/\\]+}}lib{{[/\\]+}}baremetal"
+// CHECK-V6M-C-SAME: "-L[[RESOURCE_DIR:[^"]+]]{{[/\\]+}}lib{{[/\\]+}}baremetal"
 // CHECK-V6M-C-SAME: "-T" "semihosted.lds" "-Lsome{{[/\\]+}}directory{{[/\\]+}}user{{[/\\]+}}asked{{[/\\]+}}for"
 // CHECK-V6M-C-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m.a"
 // CHECK-V6M-C-SAME: "-o" "{{.*}}.o"
 
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     -target armv6m-none-eabi \
 // RUN:     -nostdlibinc -nobuiltininc \
 // RUN:     --sysroot=%S/Inputs/baremetal_arm \