CONFIGURE: pass correct toolchain values to chromium build

also set V=1 which forces verbose build output, respect MAKEOPTS and
MAKE/CMAKE_BUILD_TOOL instead of hardcoded "make"

fixes #389

NOTE: this is a candidate for the stable branches

v2: add fixes and NOTE
cmake: build cef in jobserver mode

fixes #415

also lower cmake version requiernemt to 2.8.2

NOTE: this is a candidate for the stable branches

v2: remove include of ProcessorCount
Merge pull request #517 from karolherbst/cef_improvements

Cef improvements