[Qgis-user] Building 3.10.0 from source: cannot find header

[Rich Shepard]

Running Slackware-14.2/x86_64 here with proj-6.2.1, gdal-3.0.2, geos-3.8.0,
libgeotiff-1.5.1, and libspatialite 4.3.0.

Configuring fails here:

checking proj_api.h usability... no
checking proj_api.h presence... no
checking for proj_api.h... no
configure: error: cannot find proj_api.h, bailing out

yet the header is present:

$ locate proj_api.h
/usr/include/proj_api.h

I've run ldconfig and would appreciate ideas on how to get qgis to find the
file it seeks.

Regards,

Rich