Auto merge of #33848 - alexcrichton:android-gdb-sysroot, r=michaelwoerister

test: Use `set sysroot` for more NDK compatibility

Recent versions of the Android NDK no longer ship debuggers like
`arm-linux-androideabi-gdb`, but instead one prebuilt binary `gdb`. We can
symlink this into place at least to get our detection still working, but it now
needs to be told what the sysroot is so it can correctly do... something. Long
story short, tests didn't pass with this change and after this change they pass.

diff --cc src/tools/compiletest/src/runtest.rs
Simple merge