mapnik: Harden build. New: --with-gdal --with-geos

- Mapnik searches for py2cairo -> added dep if --with-cairo
- Explicitly give includes and libs for icu, boost, proj,
  jpeg, libtif, and cairo
- pkg-config is not only used for cairo -> moved it out
  of the `if build.include? 'with-cairo'` block

Closes #17032.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>