Fix bad behavior when --cppopts unspecified

Because I wasn't specifying --cppopts, 'cppopts opts' was "", so the first value given to language-c's runPreprocessor was [""]. This caused language-c to run gcc with ["-o","/tmp/xxx.i","-E","xxx.h",""] (note the final ""), which caused gcc to die with "error: : No such file or directory".