There is very little benefit to having another layer of moz.build files, and
removing them will speed up the build a minimal amount. It also paves the way
for removing TEST_DIRS, which could simplify the build system somewhat.
Every directory with a jar.mn now has JAR_MANIFESTS defined in its
moz.build file.
We also removed the may_skip special consideration of jar.mn files
because this information is now available during tier traversal by the
reader courtesy of the variables being present in moz.build files.
--HG--
extra : rebase_source : 21049b15e6bd9cf65b0805ccaccc4ba5aae93c98
extra : amend_source : 0b1ea866d725beef92d37c6f6d475369ac002e19
