test: fix MIPS driver tests

The tests attempt to validate the invocation of the assembler program with the
integrated assembler disabled.  However, the match pattern for the negative
tests are lax and will match both the driver invocation as well as the assembler
invocation.  Make the tests more strict by ensuring that we only match the
assembler invocation.
clang: forward -no-integrated-as from the driver

Forward the -no-integrated-as option to -cc1 rather than simply invoking the
appropriate tool.  This is useful since this option has been overloaded to
permit disabling of parsing inline assembly at the MC layer.

This re-applies the previous version of the patch with a renaming of the driver
option to the public name rather than the internal name (-target vs -triple).
The actual failure is fixed separately of an overly aggressive negative pattern
match in the MIPS driver tests.  It also fixes the incorrect test for targets
that have the integrated assembler disabled by default.