Update gpdb.cmake

Author: tuhaihe

gpcontrib/diskquota/cmake/Gpdb.cmake

@@ -40,14 +40,15 @@ exec_program(${PG_CONFIG} ARGS --libdir OUTPUT_VARIABLE PG_LIB_DIR)
 exec_program(${PG_CONFIG} ARGS --pgxs OUTPUT_VARIABLE PG_PGXS)
 get_filename_component(PG_HOME "${PG_BIN_DIR}/.." ABSOLUTE)
 
-# If PG_SRC_DIR is provided (in-tree build), use source tree include paths
-# This is necessary because pg_config --includedir returns the install path,
-# which doesn't exist yet during in-tree builds
+# If PG_SRC_DIR is provided (in-tree build), use source tree paths
+# This is necessary because pg_config returns install paths,
+# which don't exist yet during in-tree builds
 if(PG_SRC_DIR)
     set(PG_INCLUDE_DIR "${PG_SRC_DIR}/src/include")
     set(PG_INCLUDE_DIR_SERVER "${PG_SRC_DIR}/src/include")
-    # libpq headers are in src/interfaces/libpq in source tree
+    # libpq headers and library are in src/interfaces/libpq in source tree
     set(PG_INCLUDE_DIR_LIBPQ "${PG_SRC_DIR}/src/interfaces/libpq")
+    set(PG_LIB_DIR "${PG_SRC_DIR}/src/interfaces/libpq")
     message(STATUS "In-tree build: using source include path '${PG_INCLUDE_DIR}'")
 else()
     # Standalone build: try to derive PG_SRC_DIR from Makefile.global (optional)