Add gau2grid as dependency in GauXC config file (#169)

Author: awvwgk

CMakeLists.txt

@@ -59,7 +59,7 @@ set( GAUXC_HAS_CUDA       FALSE CACHE BOOL "" FORCE )
 set( GAUXC_HAS_HIP        FALSE CACHE BOOL "" FORCE )
 set( GAUXC_HAS_MPI        FALSE CACHE BOOL "" FORCE )
 set( GAUXC_HAS_OPENMP     FALSE CACHE BOOL "" FORCE )
-set( GAUXC_HAS_GAU2GRID   FALSE CACHE BOOL "" FORCE )
+set( GAUXC_HAS_GAU2GRID   FALSE CACHE STRING "" FORCE )
 set( GAUXC_HAS_HDF5       FALSE CACHE BOOL "" FORCE )
 set( GAUXC_HAS_MAGMA      FALSE CACHE BOOL "" FORCE )
 set( GAUXC_HAS_NCCL       FALSE CACHE BOOL "" FORCE )

cmake/gauxc-config.cmake.in

@@ -30,6 +30,10 @@ if(GAUXC_HAS_OPENMP)
   find_dependency( OpenMP )
 endif()
 
+if( GAUXC_HAS_GAU2GRID STREQUAL "External" )
+  find_dependency( gau2grid )
+endif()
+
 if( GAUXC_HAS_HOST )
   if(GAUXC_BLAS_IS_LP64)
     set( _blas_components lp64 )

cmake/gauxc-gau2grid.cmake

@@ -28,16 +28,21 @@ if( GAUXC_ENABLE_GAU2GRID )
         if( NOT TARGET gau2grid::gg )
           message( STATUS "Something Went Horribly Wrong With Gau2Grid discovery!" )
         endif()
-      
+
+        set( GAUXC_HAS_GAU2GRID External CACHE STRING "GauXC has Gau2Grid and will build bindings" FORCE )
       else()
 
         message( STATUS "Building Pregenerated Gau2grid" )
         add_subdirectory( ${PROJECT_SOURCE_DIR}/external/gau2grid ${PROJECT_BINARY_DIR}/external/gau2grid )
+        set( GAUXC_HAS_GAU2GRID Vendored CACHE STRING "GauXC has Gau2Grid and will build bindings" FORCE )
 
       endif()
 
+    else()
+      set( GAUXC_HAS_GAU2GRID External CACHE STRING "GauXC has Gau2Grid and will build bindings" FORCE )
     endif() # If not discoverable
+  else()
+    set( GAUXC_HAS_GAU2GRID External CACHE STRING "GauXC has Gau2Grid and will build bindings" FORCE )
   endif() # If target not present
 
-  set(GAUXC_HAS_GAU2GRID TRUE CACHE BOOL "GauXC has Gau2Grid and will build bindings" FORCE)
 endif() # If enabled