relative path somehow got broken

full path seems to work and the patch anyway tries to convert relpath back to full path
fix #981

Author: doutriaux1

CMake/cdat_modules_extra/ESMP_install_step.cmake.in

@@ -2,9 +2,8 @@
 include(@cdat_CMAKE_BINARY_DIR@/cdat_common_environment.cmake)
 
 file(GLOB_RECURSE ESMP_esmfmkfile "@cdat_EXTERNALS@/lib/libO/*.mk")
-file(RELATIVE_PATH _rel_path @PYTHON_SITE_PACKGES_PREFIX@/ESMP/src ${ESMP_esmfmkfile})
 
-set(ENV{ESMFMKFILE} ${_rel_path})
+set(ENV{ESMFMKFILE} ${ESMP_esmfmkfile})
 foreach( item ${ESMP_esmfmkfile})
   message("item " ${item})
 endforeach( item ${ESMP_esmfmkfile})