Android.mk: Fix export of static libraries with PRIVATE dependencies

The `LINK_ONLY` generator expression is used to represent private
dependencies of static libraries in their `INTERFACE_LINK_LIBRARIES`
property value.  Fix evaluation of generator expressions during export
to support the `LINK_ONLY` genex.  Extend the RunCMake.AndroidMK test
with a case for this.
Status Job ID Name Coverage
  External
passed cdash

passed cmake-dash3win7-windows-release-ninja

passed cmake-hythloth-linux-debug-makefiles+sphinx

passed cmake-hythloth-linux-release-lint-iwyu-tidy

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-release-makefiles

passed cmake-terfin-windows-release-vs2017

passed ghostflow-branch-check-master

passed ghostflow-commit-check

passed ghostflow-stager

passed cmake-dash3win7-windows-release-ninja

passed cmake-dash3win7-windows-release-ninja

passed cmake-dash3win7-windows-release-ninja

passed cmake-dash3win7-windows-release-ninja

01:13:55

passed cmake-hythloth-linux-debug-makefiles+sphinx

passed cmake-hythloth-linux-debug-makefiles+sphinx

00:45:22

passed cmake-hythloth-linux-debug-makefiles+sphinx

passed cmake-hythloth-linux-debug-makefiles+sphinx

passed cmake-hythloth-linux-release-lint-iwyu-tidy

00:21:20

passed cmake-hythloth-linux-release-lint-iwyu-tidy

passed cmake-hythloth-linux-release-lint-iwyu-tidy

passed cmake-hythloth-linux-release-lint-iwyu-tidy

passed cmake-moonshade-osx-debug-ninja

00:15:39

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-release-makefiles

passed cmake-moonshade-osx-release-makefiles

00:11:17

passed cmake-moonshade-osx-release-makefiles

passed cmake-moonshade-osx-release-makefiles

passed cmake-terfin-windows-release-vs2017

00:41:36

passed cmake-terfin-windows-release-vs2017

passed cmake-terfin-windows-release-vs2017

passed cmake-terfin-windows-release-vs2017

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager