Include -lpthread on the link line automatically only for C++

Include -lpthread on the link line automatically only for C++

It's not necessary for C-only programs, only when using libc++.

Use %clangxx rather than %clang in the C++ tests because just changing
the language (-x c++) doesn't change the linker behavior (i.e. the
CCCIsCXX() check).

R=jvoung@chromium.org
BUG= https://code.google.com/p/nativeclient/issues/detail?id=4088

Committed: a46d3ebfd8f295a32e2dab6241d207e04302b483

[jvoung (off chromium), 2015-03-04 17:20:10]

otherwise LGTM

https://codereview.chromium.org/964923003/diff/1/test/Driver/nacl-direct.c
File test/Driver/nacl-direct.c (right):

https://codereview.chromium.org/964923003/diff/1/test/Driver/nacl-direct.c#ne...
test/Driver/nacl-direct.c:53: // CHECK-ARM: "-internal-isystem"
"{{.*}}/../arm-nacl/include"
could CHECK-ARM-NOT: "-lpthread", etc.

[Derek Schuff, 2015-03-04 17:39:35]

https://codereview.chromium.org/964923003/diff/1/test/Driver/nacl-direct.c
File test/Driver/nacl-direct.c (right):

https://codereview.chromium.org/964923003/diff/1/test/Driver/nacl-direct.c#ne...
test/Driver/nacl-direct.c:53: // CHECK-ARM: "-internal-isystem"
"{{.*}}/../arm-nacl/include"
On 2015/03/04 17:20:09, jvoung wrote:
> could CHECK-ARM-NOT: "-lpthread", etc.

Done.

[Derek Schuff, 2015-03-04 17:44:35]

Committed patchset #2 (id:20001) manually as
a46d3ebfd8f295a32e2dab6241d207e04302b483 (tree was closed).