CI: split i686-msvc job to two free runners

Author: marcoieni

src/bootstrap/mk/Makefile.in

@@ -97,6 +97,11 @@ tidy:
 prepare:
 	$(Q)$(BOOTSTRAP) build --stage 2 --dry-run
 
+# Set of tests that represent around half of the time of the test suite.
+# Used to split tests across multiple CI runners.
+STAGE_2_TEST_SET1 := test --stage 2 --skip=compiler --skip=src
+STAGE_2_TEST_SET2 := test --stage 2 --skip=tests --skip=coverage-map --skip=coverage-run --skip=library --skip=tidyselftest
+
 ## MSVC native builders
 
 # this intentionally doesn't use `$(BOOTSTRAP)` so we can test the shebang on Windows
@@ -105,16 +110,20 @@ ci-msvc-py:
 ci-msvc-ps1:
 	$(Q)$(CFG_SRC_DIR)/x.ps1 test --stage 2 --skip tidy
 ci-msvc: ci-msvc-py ci-msvc-ps1
+ci-msvc-py-set1:
+	$(Q)$(CFG_SRC_DIR)/x.py $(STAGE_2_TEST_SET1)
+ci-msvc-ps1-set2:
+	$(Q)$(CFG_SRC_DIR)/x.ps1 $(STAGE_2_TEST_SET2)
 
 ## MingW native builders
 
 # Set of tests that should represent half of the time of the test suite.
 # Used to split tests across multiple CI runners.
 # Test both x and bootstrap entrypoints.
 ci-mingw-x:
-	$(Q)$(CFG_SRC_DIR)/x test --stage 2 --skip=compiler --skip=src
+	$(Q)$(CFG_SRC_DIR)/x $(STAGE_2_TEST_SET1)
 ci-mingw-bootstrap:
-	$(Q)$(BOOTSTRAP) test --stage 2 --skip=tests --skip=coverage-map --skip=coverage-run --skip=library --skip=tidyselftest
+	$(Q)$(BOOTSTRAP) $(STAGE_2_TEST_SET2)
 ci-mingw: ci-mingw-x ci-mingw-bootstrap
 
 .PHONY: dist

src/ci/github-actions/jobs.yml

@@ -448,11 +448,18 @@ auto:
       SCRIPT: make ci-msvc
     <<: *job-windows-8c
 
-  - name: i686-msvc
+  # i686-msvc is split into two jobs to run tests in parallel.
+  - name: i686-msvc-1
     env:
       RUST_CONFIGURE_ARGS: --build=i686-pc-windows-msvc
-      SCRIPT: make ci-msvc
-    <<: *job-windows-8c
+      SCRIPT: make ci-msvc-py-set1
+    <<: *job-windows
+
+  - name: i686-msvc-2
+    env:
+      RUST_CONFIGURE_ARGS: --build=i686-pc-windows-msvc
+      SCRIPT: make ci-msvc-ps1-set2
+    <<: *job-windows
 
   # x86_64-msvc-ext is split into multiple jobs to run tests in parallel.
   - name: x86_64-msvc-ext1