sourcery-tuning: fix -march=armv5e failures
The most common failure case was qemuarm. Currently, ARMPKGSFX_THUMB is used
in TUNE_CCARGS, and it only includes 't' when ARM_INSTRUCTION_SET=thumb.
Bypass that check for armv5, as we need -march=armv5te rather than
-march=armv5t, but we still want -mthumb removed when appropriate.
Fixes #86
Signed-off-by: Christopher Larson <chris_larson@mentor.com>