AFAIK gyp is dead and everything uses gn now, but bots still define a GYP_DEFINES environment variable in the gclient_runhooks step. Even worse, the values don't match up with the gn args the bot is using in generate_build_files step.

Example:
https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Ftryserver.chromium.android%2Fandroid_compile_dbg%2F244962%2F%2B%2Frecipes%2Fsteps%2Fgclient_runhooks__with_patch_%2F0%2Fstdout
shows:
 GYP_DEFINES: OS=android component=static_library dcheck_always_on=1 fastbuild=1 ffmpeg_branding=Chrome gomadir=/b/c/goma_client proprietary_codecs=1 target_arch=arm use_goma=1


https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Ftryserver.chromium.android%2Fandroid_compile_dbg%2F244962%2F%2B%2Frecipes%2Fsteps%2Fgenerate_build_files__with_patch_%2F0%2Fstdout
shows:
Writing """\
ffmpeg_branding = "Chrome"
goma_dir = "/b/c/goma_client"
is_component_build = true
is_debug = true
proprietary_codecs = true
strip_absolute_paths_from_debug_symbols = true
symbol_level = 1
target_os = "android"
use_goma = true
""" to /b/c/b/android/src/out/Debug/args.gn.


This is super confusing. I couldn't repro the failure, but it was because I was doing a static build due to looking at the old GYP_DEFINES and the bot is actually doing a component build.

Even if the GYP_DEFINES are correct, I was wasting time manually converting them to GN equivalents. We should just remove the GYP_DEFINES so that it's obvious they aren't used anymore.