Add error log for missing arguments when compiling @VintfStability

The error log did not mention the required '--structured' flag when it
was missing. This now differentiates between missing the '--structured'
flag and the '--stability vintf' flags.

Test: atest aidl_unittests aidl_integration_test
Change-Id: I3b09f8f4106b729aade90b9526553905a5a8f681
2 files changed