m3_option(x) adds option x to the set of arguments passed to the compiler.
Specifically, m3_option adds x to the M3OPTIONS variable . x should be a single string preceded with a hyphen, e.g. m3_option("-O").
Some of the more useful compiler options include:
-why Explain why each compilation is needed (default). -commands Print the compilation commands as they are started. -verbose Print what happens to each file. -times Print a breakdown of elapsed time. -g Generate debugging symbols (default). -O Optimize code. -keep Preserve intermediate files. -once Don't recompile modules with new opaque info.
All the compiler options may also be specified on the command line.