Bug 1380605 - modifications to build openh264 v1.7.1, r=catlee

Notable changes
* ensure we run dump-symbols and upload actions on all platforms
* On android:
 * add configuration and support for aarch64
 * set min_sdk levels to match Fennec builds
 * use a full copy of the r11c ndk (our truncated one was missing toolchains we needed) and set NDKROOT when calling build
 * ensure the tooltool provided sdk is on the PATH
* on linux copy tooltool.py into the mock environment, so we can get dump_syms from tt
* remove macosx32 config as we've deprecated that in Firefox builds
* update dump_syms to recent m-c, notably for aarch64 support on linux
 * on linux rev e365137fa61bfd729617ba1ebf9f1ed79facd1f2 (via try 0f72a5c28be1cdc2f3bdfaafdf3826254f6ba077)
 * on mac rev e365137fa61bfd729617ba1ebf9f1ed79facd1f2 (via compile on a bld-lin-r5)
 * on windows rev a4a448ba7f187069fce916ee234a06cbb0d06f80 (via try dc8b121e3c08e8022d62c0fa1951dd3dc4d6f7cc)
* switch to Visual Studio 2015 Update 3 on win32/win64 to match Firefox
 * many updates to environement variables
 * painful to get win64 right to run win32 dump_syms.exe, but that's why the x86 redist is on teh PATH
* unwind the changes to get_output_from_command() in v1.6 patch to avoid affecting other builds, and use query_env() which has this support already
* add a scp_upload_directory since we don't have rsync on windows, use that to talk to the ffxbld upload host (not a long term solution but OK for now)

Applies on top of https://reviewboard.mozilla.org/r/64022/diff/4#index_header

MozReview-Commit-ID: B3NiWFvr2oR