rippled: develop build error: target pattern contains no '%'

While attempting to rebase #3197 I am encountered an error in (what I am guessing is) the new GRPC build logic. I switched over to a clean copy of the latest develop branch (commit 90d9ca901d - “Set version to 1.5.0-b3”), deleted all outstanding generated files and tried again to no avail. The complete error is below:

[ 22%] Performing build step for 'grpc_src'
Build output for /home/mmorsi/Workspace/rippled/.nih_c/unix_makefiles/GNU_9.2.1/Release/src/grpc_src-stamp/grpc_src-build : 
[  0%] Built target address_sorting
[  3%] Built target gpr
[  3%] Built target grpc_plugin_support

CMakeFiles/gen_percent_encoding_tables.dir/build.make:82: *** target pattern contains no '%'.  Stop.
gmake[4]: *** [CMakeFiles/Makefile2:257: CMakeFiles/gen_percent_encoding_tables.dir/all] Error 2
gmake[4]: *** Waiting for unfinished jobs....
gmake[3]: *** [Makefile:130: all] Error 2
CMake Error at /home/mmorsi/Workspace/rippled/.nih_c/unix_makefiles/GNU_9.2.1/Release/src/grpc_src-stamp/grpc_src-build-Release-impl.cmake:9 (message):
  Command failed (2):

   '/usr/bin/cmake' '--build' '.' '--config' 'Release' '--parallel' '4' ''

CMake Error at /home/mmorsi/Workspace/rippled/.nih_c/unix_makefiles/GNU_9.2.1/Release/src/grpc_src-stamp/grpc_src-build-Release.cmake:23 (message):
  Command failed: 1

   '/usr/bin/cmake' '-Dmake=' '-Dconfig=' '-P' '/home/mmorsi/Workspace/rippled/.nih_c/unix_makefiles/GNU_9.2.1/Release/src/grpc_src-stamp/grpc_src-build-Release-impl.cmake'

  See above

make[2]: *** [CMakeFiles/grpc_src.dir/build.make:114: ../.nih_c/unix_makefiles/GNU_9.2.1/Release/src/grpc_src-stamp/grpc_src-build] Error 1
make[1]: *** [CMakeFiles/Makefile2:723: CMakeFiles/grpc_src.dir/all] Error 2
make: *** [Makefile:130: all] Error 2

The error seems to indicate the problem is occurring in the build configuration WRT the new GRPC logic, though can’t say for sure what the root cause is. Inspecting further, the referenced file CMakeFiles/gen_percent_encoding_tables.dir/build.make does not seem to exist locally. Googling it a bit, it seem to reference a syntax issue in a build target, though perhaps someone “more in the know” w/ recent grpc additions / build modifications could advise further.

Local system: Fedora Linux (version 30) Cmake: Version 3.14.5 Let me know if I can help by providing any more info. Thank you.