Fix name of Docker image generated via build-gramine

User must provide the output Docker image name in `build-gramine <name>`
command but the generated image prepends `gsc-` which leads to a
confusion about what image name should be specified in config file.

With this commit, the generated Docker image has the name exactly as
specified in the `build-gramine` argument (without `gsc-` prepended).

Signed-off-by: jkr0103 <jitender.kumar@intel.com>

gsc.py

@@ -294,10 +294,17 @@ def gsc_build(args):
 
     config = yaml.safe_load(args.config_file)
     if 'Image' in config['Gramine']:
-        gramine_image_name = gsc_image_name(config['Gramine']['Image'])
+        gramine_image_name = config['Gramine']['Image']
         if get_docker_image(docker_socket, gramine_image_name) is None:
-            print(f'Cannot find base-Gramine Docker image `{gramine_image_name}`.')
-            sys.exit(1)
+            # TODO: Drop support for old style base-Gramine Docker image name with GSC v1.8 release
+            if get_docker_image(docker_socket, gsc_image_name(gramine_image_name)) is None:
+                print(f'Cannot find base-Gramine Docker image `{gramine_image_name}`.')
+                sys.exit(1)
+
+            config['Gramine']['Image'] = gsc_image_name(gramine_image_name)
+            print(f'Warning: The base-Gramine Docker image `{gramine_image_name}` was generated by'
+                  ' an older version of GSC. Please re-build this image using this GSC version.'
+                  ' This warning will become an error in the future.')
 
     print(f'Building unsigned graminized Docker image `{unsigned_image_name}` from original '
           f'application image `{original_image_name}`...')
@@ -397,7 +404,7 @@ def gsc_build(args):
 
 # Command 2: Build a "base Gramine" Docker image with the compiled runtime of Gramine.
 def gsc_build_gramine(args):
-    gramine_image_name = gsc_image_name(args.image)  # output base-Gramine image name
+    gramine_image_name = args.image  # output base-Gramine image name
     tmp_build_path = gsc_tmp_build_path(args.image)  # pathlib obj with build artifacts
 
     docker_socket = docker.from_env()

templates/Dockerfile.common.build.template

@@ -1,6 +1,6 @@
 # Include previously-prepared Docker image with Gramine (if any) or compile Gramine from sources
 {% if Gramine.Image %}
-FROM gsc-{{Gramine.Image}} AS gramine
+FROM {{Gramine.Image}} AS gramine
 {% else %}
 {% include compile_template %}
 {% endif %}