To make it build again with CMake + Android 20 and earlier.
8e34505776 synced `getpwuid_r()` detection
in cmake with autotools. It means cmake started detecting it with
Android <21 just like autotools, and thus cmake builds also need to
tackle the missing declaration with old Android SDK versions. Use a PP
solution, allowing to drop the autotools-specific on used before this
patch.
Follow-up to 8e34505776#15164
Follow-up to 9c33813d83#2609
Ref: #2058Closes#15871
0f1b23e960