Build: option to time individual compile commands (#3194)
Build: option to time individual compile commands (#3194)

This adds a new cmake variable in our build system, TIME_COMMANDS,
that when set ON will adjust the compile and link rule launch to
include a time command. This is probably only useful when also setting
`CMAKE_BUILD_PARALLEL_LEVEL=1` so that build are happening serially.
The use case is to investigate how long each module takes to compile,
for optimizing the build.
OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio