prebuilt-common.sh: get_prebuilt_install_prefix
David Turner authored
This patch adds a new function to prebuilt-common.sh that can
return the install location of prebuilt host binaries. It
currently is: $NDK/prebuilt/$HOST_TAG/

This will be used to store host binaries, like the Win32 versions
of GNU Make, Awk, Sed and others.

Change-Id: I8a543b4f4d6b728e13046f3759a5b8584cea6001
9ac252a1