Allow mongo-c and json-c drivers installation at custom locations.

autogen.sh helps in avoiding manual installation and automates the
download and installation of the appropriate drivers and libraries
including mongo-c and json-c driver. But, these drivers get
installed at the default locations e.g. /usr/lib/, and user might
not have permission to write in this directory. This results in
autogen.sh failure. Use environment variables MONGOC_INSTALL_DIR
and JSONC_INSTALL_DIR in autogen.sh to set CMAKE_INSTALL_PREFIX to
allow custom directory installation for these drivers where the user
might have permission.

Reported on GitHub through issue #152 by user pgloader.

FDW-406, Vaibhav Dalvi, reviewed by Jeevan Ladhe,
tested by Rajkumar Raghuwanshi.

Author: jeevanladhe

README.md

@@ -96,7 +96,34 @@ different type of MongoDB drivers and supported libraries. If you want
 to avoid the manual steps, there is a shell script available which will
 download and install the appropriate drivers and libraries for you.
 
-Here is how it works :
+Here is how it works:
+
+To install mongo-c and json-c libraries at custom locations, you need to
+export environment variables `MONGOC_INSTALL_DIR` and `JSONC_INSTALL_DIR`
+respectively. If these variables are not set then these libraries will be
+installed in the default location. Please note that you need to have the
+required permission to install the directory whether it is custom or default.
+
+The `PKG_CONFIG_PATH` environment variable must be set to mongo-c-driver source
+directory for successful compilation as shown below,
+
+```sh
+export PKG_CONFIG_PATH=$YOUR_MONGO_FDW_SOURCE_DIR/mongo-c-driver/src/libmongoc/src:$YOUR_MONGO_FDW_SOURCE_DIR/mongo-c-driver/src/libbson/src
+```
+
+The `LD_LIBRARY_PATH` environment variable must include the path to the mongo-c
+installation directory containing the libmongoc-1.0.so and libbson-1.0.so
+files. For example, assuming the installation directory is /home/mongo-c and
+the libraries were created under it in lib64 sub-directory, then we can define
+the `LD_LIBRARY_PATH` as:
+
+```sh
+export LD_LIBRARY_PATH=/home/mongo-c/lib64:$LD_LIBRARY_PATH
+```
+
+Note: This `LD_LIBRARY_PATH` environment variable setting must be in effect
+when the `pg_ctl` utility is executed to start or restart PostgreSQL or
+EDB Postgres Advanced Server.
 
 Build with [MongoDB][1]'s legacy branch driver
    * autogen.sh --with-legacy

autogen.sh

@@ -16,6 +16,8 @@
 
 MONGOC_VERSION=1.17.3
 JSONC_VERSION=0.15-20200726
+MONGOC_INSTALL="${MONGOC_INSTALL_DIR}"
+JSONC_INSTALL="${JSONC_INSTALL_DIR}"
 
 if [ "$#" -ne 1 ]; then
     echo "Usage: autogen.sh --[with-legacy | with-master]"
@@ -71,7 +73,7 @@ function checkout_json_lib
 function install_json_lib
 {
 	cd json-c &&
-	$CMAKE_COMMAND $JSONC_CFLAGS . &&
+	$CMAKE_COMMAND -DCMAKE_INSTALL_PREFIX=$JSONC_INSTALL $JSONC_CFLAGS . &&
 	make install &&
 	cd ..
 }
@@ -82,7 +84,7 @@ function install_json_lib
 function install_mongoc_driver
 {
 	cd mongo-c-driver &&
-	$CMAKE_COMMAND -DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF -DENABLE_SSL=AUTO . &&
+	$CMAKE_COMMAND -DCMAKE_INSTALL_PREFIX=$MONGOC_INSTALL -DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF -DENABLE_SSL=AUTO . &&
 	make install &&
 	cd ..
 }