Fix for building ARM/linux using clang.

src/trusted/service_runtime/linux/nacl_bootstrap.gyp

Index: src/trusted/service_runtime/linux/nacl_bootstrap.gyp
diff --git a/src/trusted/service_runtime/linux/nacl_bootstrap.gyp b/src/trusted/service_runtime/linux/nacl_bootstrap.gyp
index c0bdc266beb92aa05ae699904e15adcf45766373..ba4e1957cddac9edf6cd95408e54a4fca9c985fa 100644
--- a/src/trusted/service_runtime/linux/nacl_bootstrap.gyp
+++ b/src/trusted/service_runtime/linux/nacl_bootstrap.gyp
@@ -156,6 +156,14 @@
               'variables': {
                 'compiler': '<!(/bin/echo -n <(android_toolchain)/*-g++)',
               }
+            }],
+            # When building for ARM default to arm-linux-gnueabi-g++ rather
+            # than g++.  This is needed when building with clang (since in
+            # this case $CC and $CXX are not set in the envrionement).

[Mark Seaborn, 2014/07/28 19:23:20]

"environment"

+            ['OS!="android" and target_arch=="arm"', {
+              'variables': {
+                'compiler': '<!(echo ${CXX:=arm-linux-gnueabi-g++})',

[Roland McGrath, 2014/07/28 19:20:51]

I don't really understand what's going on here, but hard-coding this here seems
wrong.  It's as likely to be arm-linux-gnueabihf-g++, for example.

[Mark Seaborn, 2014/07/28 19:23:20]

It's a bit counterintuitive that in order to build with clang, you have to
specify arm-gcc here.

Would this then be the only place in the Gyp build where arm-gcc gets invoked? 
And would this be the only part that requires the arm-gcc Debian package to be
installed?

Is this only needed in conjunction with another change (like
https://codereview.chromium.org/414343003/)?

Could we get this to use the same host compiler that Gyp uses?  Is there any way
to refer to CC from 'make_global_settings'?  If not, could we add another
variable to common.gypi to define this compiler?

If this is tricky to resolve, I'd suggest sending the nacl_syscall_common.c
change as a separate change.

+              }
             }, {
               'variables': {
                 'compiler': '<!(echo ${CXX:=g++})',