They are now explicit in the Bionic blueprints, and brought in through
dependencies on libc (which in turn is usually implicit through the
default system_shared_libs value). Modules that may break are cc_object
which don't depend on system_shared_libs, and those that explicitly set
system_shared_libs:[] but still assumes libc headers. In either case
the fix should be to add header_libs:["libc_headers"].
Test: Build and boot
Test: m checkbuild (on aosp_taimen and aosp_x86_64)
Bug: 153590472
Change-Id: I3217d8f36e49a987f5377866c8647f9dcccc37ce
41ab2519b4