engine.pl: Fix a recent breakage of the buildsystem generator

engine.pl: Fix a recent breakage of the buildsystem generator

Commit ade2ca0c (Do not try to remove directories when removing
old links, 2009-10-27) added an expression to a 'test' using an
'-o' or connective. This resulted in the buildsystem generator
mistaking a conditional 'rm' for a linker command. In order to
fix the breakage, we filter out all 'test' commands before then
attempting to identify the commands of interest.

Signed-off-by: Ramsay Jones <redacted>
Acked-by: Sebastian Schuberth <redacted>
Signed-off-by: Junio C Hamano <redacted>