aapt: Always use our libz

Instead of using the system libz (-lz), include our copy as a static
library. This is safer in case the system version isn't compatible.

Also removes references to -ldl -lrt -lpthread, which are now implied.

Test: m -j
Test: out/host/linux-x86/nativetest64/libaapt_tests/libaapt_tests
Test: out/host/linux-x86/nativetest64/aapt2_tests/aapt2_tests
Test: out/host/linux-x86/nativetest64/libsplit-select_tests/libsplit-select_tests
Change-Id: Icd26dc1e0d011e5b5f158e562640533c5ac34e33