Note that we already have bots that build all targets: https://build.chromium.org/p/chromium/builders/Mac/builds/19854/steps/compile/logs/stdio

We can probably just hijack these bots to also not have a system toolchain.

Due to the needs of Infra>labs, we can't get away from having a CLT install. We can, however, delete all the binaries that are needed to build Chrome, but not needed by Infra. These are:

ld, bison, gperf, otool, dsymutil, strip, ibtool, libtool, lipo, nm and strings

All try-bots are now hermetic.