Add TARGET_SUPPORTS_32_BIT_APPS to soong_config_variable:

Some modules still need to use TARGET_SUPPORTS_32_BIT_APPS to
distinguish whether they support 32-bit and 64-bit (e.g., Chrome).

Bug: 383686128
Test: m -j TrichromeLibrary-Stub
Change-Id: I65dbc20876787f750d84fa9c18b2ad38159e2d35