Use static linkage to reduce user/userdebug differences

This commit changes the linkage of `kGcovPrefixEnvVar`,
`kGcovPrefixOverrideEnvVar`, `kGcovPrefixPath`, `kSysPropHalCoverage`,
and `kSysPropInstrumentationPath` to static linkage so that they won't
be exported in userdebug build. This ensures both user and userdebug
build export the same symbol set.

Bug: 117859056
Test: libhidlbase.so builds w/o problems under userdebug build
Change-Id: Id61b827f3da1964e060db6f862132da70b29cea0
1 file changed