[NaCl SDK] Make ARM cross compiler optional until trybots get updated.

[NaCl SDK] Make ARM cross compiler optional until trybots get updated.

This change, combined with the recent revert of the SDK ARM
components on in the NaCl tree (https://codereview.chromium.org/141733005/)
should allow the SDK builders to go green again.

BUG=335303
R=binji@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=246461

[binji, 2014-01-22 22:33:46]

lgtm, w/ question

https://codereview.chromium.org/132523006/diff/1/native_client_sdk/src/build_...
File native_client_sdk/src/build_tools/build_sdk.py (right):

https://codereview.chromium.org/132523006/diff/1/native_client_sdk/src/build_...
native_client_sdk/src/build_tools/build_sdk.py:540: if
os.path.exists("/usr/bin/arm-linux-gnueabihf-gcc"):
shouldn't this just skip the arm build entirely instead if the compiler doesn't
exist?

[Sam Clegg, 2014-01-22 22:36:04]

https://codereview.chromium.org/132523006/diff/1/native_client_sdk/src/build_...
File native_client_sdk/src/build_tools/build_sdk.py (right):

https://codereview.chromium.org/132523006/diff/1/native_client_sdk/src/build_...
native_client_sdk/src/build_tools/build_sdk.py:540: if
os.path.exists("/usr/bin/arm-linux-gnueabihf-gcc"):
On 2014/01/22 22:33:47, binji wrote:
> shouldn't this just skip the arm build entirely instead if the compiler
doesn't
> exist?

The current nacl gyp files require the arm cross compiler when you in order to
build the nacl_core_sdk gyp target.

There is a NaCl side revert that removes this requirement but I'd
like to put that back once the bots have the compiler installed.

[Sam Clegg, 2014-01-23 00:58:51]

Committed patchset #1 manually as r246461 (presubmit successful).