Fix HOST_TOOLCHAIN_PREFIX

Previously HOST_TOOLCHAIN_PREFIX can't accept toolchain in arch-os-*-gcc
format.  Fix it so we can try out new host toolchain, eg.

  HOST_TOOLCHAIN_PREFIX=prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.6/bin/x86_64-linux- make

Change-Id: Ic1092593036c41d5471e788654fb4e0991dd7e40
Remove external/chromium from the 64 bit blacklist.

This isn't the same as chromium_org (which is used by the
webview). This is a 3 year old snapshot of the net stack which
compiles under 64 bit. It's currently used on aosp master by
libstagefright_chromium_http.

This project can be removed if the changes that remove the
chromium dependency are cherry-picked to aosp/master.

Change-Id: I5d0f9ed03ea9842b47d980d77ea32bc7a3f6998f
Merge "Remove external/chromium from the 64 bit blacklist."
Revert "Remove external/chromium from the 64 bit blacklist."

This reverts commit 27bf51144af3513605cff421beb39a556599eb42.

Change-Id: Ic7e4fff8f87342a248172c2fc0d1358b4db1c25c
Merge "Revert "Remove external/chromium from the 64 bit blacklist.""
Merge "Fix HOST_TOOLCHAIN_PREFIX"
Merge remote-tracking branch 'origin/master'