CI: Avoid OOM on coverage merge in GitHub actions

.github/workflows/reusable-test.yml

@@ -107,7 +107,7 @@ jobs:
       - name: Combine code coverage data
         if: ${{ inputs.dev-gcov }}
         run: |
-          make coverage-combine
+          make coverage-combine FASTCOV_JOBS=2
           mv obj_coverage/verilator.info obj_coverage/verilator-${{ inputs.suite }}.info
           ls -lsha obj_coverage
 

Makefile.in

@@ -710,7 +710,8 @@ override undefine COVERAGE_BASE # Use the above variabels instead
 
 # 'fastcov' setup
 FASTCOV := nodist/fastcov.py
-FASTCOV_OPT := -j $(shell nproc)
+FASTCOV_JOBS ?= $(shell nproc)
+FASTCOV_OPT := -j $(FASTCOV_JOBS)
 FASTCOV_OPT += --gcov $(GCOV)
 FASTCOV_OPT += --lcov
 FASTCOV_OPT += --process-gcno