Because proj4 is not properly maintained, proj4 will not install where proj_api.h is absent. This can be fixed (add "-DACCEPT_USE_OF_DEPRECATED_PROJ_API_H" to PKG_CPPFLAGS) for PROJ 6, but PROJ 7 due in 10 months will remove this option. Please ask Simon to address this. I noticed this when running reverse dependency checks.
Because proj4 is not properly maintained, proj4 will not install where proj_api.h is absent. This can be fixed (add "-DACCEPT_USE_OF_DEPRECATED_PROJ_API_H" to PKG_CPPFLAGS) for PROJ 6, but PROJ 7 due in 10 months will remove this option. Please ask Simon to address this. I noticed this when running reverse dependency checks.