Makefile: Support VERBOSE,QUIET,GDB in RUN_TEST

Allow the user to trigger a "verbose" test (in the sense of
run_test.sh's -v) through VERBOSE and/or to avoid redirecting the test's
output to a log file through QUIET and/or to allow a GDB connection
through GDB:

    make VERBOSE=1 test-boot              # prints commands
    make QUIET=0 test-crosvm-helloworld   # prints VM outputs to screen
    make GDB=1 test-boot                  # QEMU waits for GDB
    make QUIET=0 VERBOSE=1 test-boot      # they can be combined

Bug: 195395681
Test: make VERBOSE=<?> QUIET=<?> GDB=<?> test-boot
Change-Id: I73b860d141b663cb22d4e23dc927f6fadc57e31b
1 file changed
tree: 30bbaba1b4df01c139aca88312cac57cf821de0f
  1. aarch64/
  2. crosvm/
  3. cuttlefish/
  4. kvm-unit-tests/
  5. common.inc
  6. Makefile