CI: Use git hash as version number for custom gateware CI.

BeagleV-Fire uses the PolarFire-Soc IAP feature to reprogram the
SoC-FPGA from Linux. The IAP mode used only actually programs the device
if the Libero design version is different from the one in the currently
programmed FPGA design.
This change to the gateware builder uses the gateware repo's git hash to
generate a Libero design version number which will be different with each
push to a forked gateware repository. This results in the bitstream
generated by the CI to successfully reprogram the SoC-FPGA after each
change to the gateware source code.

build-bitstream.py

@@ -275,15 +275,27 @@ def get_libero_script_args(source_list):
 
 
 def get_design_version(source_list):
-    with open(source_list) as f:  # open the yaml file passed as an arg
-        data = yaml.load(f, Loader=yaml.FullLoader)
-        unique_design_version = data.get("gateware").get("unique-design-version")
-        f.close()
-    if unique_design_version is None:
-        unique_design_version = "65.53.5"
-    
-    udv_sl = unique_design_version.split(".")
-    design_version = (int(udv_sl[0]) * 1000) + (int(udv_sl[1]) * 10) + int(udv_sl[2])
+    if "custom-fpga-design" in source_list:
+        #
+        # Ensure every CI gateware build uses a unique version number for gateware programming to
+        # be successful (IAP only re-programs the FPGA if the Libero design version is different
+        # from the one already programmed in the FPGA).
+        # This is required for forked repos.
+        #
+        git_hash = subprocess.check_output(['git', 'rev-parse', '--short', 'HEAD'])
+        git_hash_hex = git_hash.decode('ascii').strip("'")
+        git_hash_dec = int(git_hash_hex, 16) % 65535
+        design_version = str(git_hash_dec)
+    else:
+        with open(source_list) as f:  # open the yaml file passed as an arg
+            data = yaml.load(f, Loader=yaml.FullLoader)
+            unique_design_version = data.get("gateware").get("unique-design-version")
+            f.close()
+        if unique_design_version is None:
+            unique_design_version = "65.53.5"
+
+        udv_sl = unique_design_version.split(".")
+        design_version = (int(udv_sl[0]) * 1000) + (int(udv_sl[1]) * 10) + int(udv_sl[2])
 
     print("design_version: ", design_version)
     return str(design_version)