pkgconfig Libs ends up with:

Libs: -Wl,-z,relro -lm -ljasper
Libs: -L/usr/lib64 -Wl,-z,relro -lm -ljasper -lgrib_api_f90 -lgrib_api

Which is incorrect in a couple ways:

• it should not specify LDFLAGS, only -L
• for dynamic linking no other libraries should be specified. For static linking they can be specified in Libs.private (and @LIBS@ should come afer).
• The grib_api.pc file does not list -lgrib_api or -L

Also Cflags should only contain the needed -I${includedir}.