Fixed file extention for minidump_upload in tools_linux.gypi

Bug:
Change-Id: I02ceca2ff7cb87bb2b8f0cf02d31f9ab6d46a8da
src/tools/linux/tools_linux.gypi was using 'symupload/minidump_upload.m' whereas it should have been 'symupload/minidump_upload.cc' for linux. '.m' is for mac.
Reviewed-on: https://chromium-review.googlesource.com/840622
Reviewed-by: Mike Frysinger <vapier@chromium.org>

src/tools/linux/tools_linux.gypi

diff --git a/src/tools/linux/tools_linux.gypi b/src/tools/linux/tools_linux.gypi
index 1c15992..020e4c1 100644
--- a/src/tools/linux/tools_linux.gypi
+++ b/src/tools/linux/tools_linux.gypi
@@ -58,7 +58,7 @@
       'target_name': 'minidump_upload',
       'type': 'executable',
       'sources': [
-        'symupload/minidump_upload.m',
+        'symupload/minidump_upload.cc',
       ],
       'dependencies': [
         '../common/common.gyp:common',