apex uses the first arch variant of prebuilt_etc modules

prebult_etc module type does not respect prefer32, i.e. its primary arch
is 64-bit on 64/32-bit device even when built with TARGET_PREFER_32_BIT
is true. However, the apex module type respects prefer32 and therefore
when TARGET_PREFER_32_BIT is true its primary arch becomes 32-bit. Then
the problem is that the apex tries to depend on 32-bit variant of the
prebuilt_etc modules which don't exist.

Fixing the problem by force using the first arch of the device when
adding dependencies to prebuilt_etc modules.

Bug: 144532908
Test: choosecombo 1 aosp_arm64 userdebug; TARGET_PREFER_32_BIT=true m;
Change-Id: I7642c57b05a837495587bbe4d3589d8549607862