build: Fix failed to assign a module name different with it's file name to a prebuilt module

Build system can not find the dependent library if assigning a
multi-prebuilt which module name is different with it's library
file name as following:
    PREBUILT_LIBS := libabc_debug:libabc.a

Change-Id: I05bdc8cebcabf74195198e3cefa1b8923f87d406
1 file changed