Fix overriding commands warnings/error

On mac, where the x86_64 architecture is disabled, and on linux when the
ART_BUILD_HOST_[N]DEBUG=false flags are set (or even the TARGET versions),
the modules referenced here aren't defined. Due to the text processing,
we end up with multiple rules defining the 'Uncompressed', 'Stripped',
etc targets:

art/build/Android.gtest.mk:97: error: overriding commands for target
`Stripped', previously defined at art/build/Android.gtest.mk:93`

These are becoming errors in this CL:

https://android-review.googlesource.com/c/platform/build/+/657896

Bug: 77611511
Test: on mac: m nothing
Test: on linux: ART_BUILD_HOST_DEBUG=false ART_BUILD_HOST_NDEBUG=false \
  ART_BUILD_TARGET_DEBUG=false ART_BUILD_TARGET_NDEBUG=false m nothing
Test: out/build-aosp_arm.ninja is the same (on linux with no args)
Change-Id: I0fec90398839fb6e3cc6443e2e37f934401dc177