For the x86_arm target, which uses two 32-bit architectures, x86
libraries should be installed into ".../lib", and arm libraries should
be installed into ".../lib/arm".
This shouldn't be necessary for binaries, but non-native binaries aren't
supported in Make right now, so we can revisit this once it's necessary.
Change-Id: I4d883c85d3ef4945ff6149d9c4fc81af5023e12b
Some more common makevars methods were required in order to remove the
"-isystem" prefixes from the toolchain.IncludeFlags() value. In Make,
the -isystem is prepended at time of use, not in TARGET_C_INCLUDES
itself.
Change-Id: If07e69ddb7357d11c7dd48ab60f503d219f29de8