libc/glibc: Add CUSTOM version and CUSTOM_LOCATION config options and GetCustom

CUSTOM_LOCATION config options only presented in menuconfig if component
CUSTOM version selected.

Signed-off-by: David Holsgrove <david.holsgrove@xilinx.com>
libc/eglibc: Add CUSTOM version and CUSTOM_LOCATION config options and GetCustom

CUSTOM_LOCATION config options only presented in menuconfig if component
CUSTOM version selected.

Signed-off-by: David Holsgrove <david.holsgrove@xilinx.com>
libc/{,e}glibc: If using custom {e}glibc, dont extract or patch

If custom {e}glibc is being used, no need to carry out the
extract or patching phase of scripts/build/libc/glibc-eglibc.sh-common

Signed-off-by: David Holsgrove <david.holsgrove@xilinx.com>
Merge pull request #6 from davidholsgrove/libc_custom_location

Libc custom location