ci: add a problem matcher support, to get error/warning/notice annotations in V CI jobs (#22790)

.github/problem-matchers/register_all.vsh

@@ -0,0 +1,19 @@
+// The task of this program, is to register all available .json files
+// in this folder with Github Actions, so that it can make annotations
+// for all found notices/warnings/errors produced by the V compiler
+// while running the CI jobs.
+// Those annotations provide a way to get a quick overview for failures,
+// without having to scroll into the detailed logs produced by each job.
+
+const github_job = getenv('GITHUB_JOB')
+
+if github_job == '' {
+	exit(0)
+}
+
+dump(github_job)
+chdir(@VEXEROOT)!
+for f in walk_ext('.github/problem-matchers/', '.json').sorted() {
+	println('::add-matcher::${real_path(f)}')
+	println('registered matcher: `${f}`')
+}

.github/problem-matchers/v.json

@@ -0,0 +1,18 @@
+{
+    "__comment": "Based on https://github.com/python/cpython/blob/main/.github/problem-matchers/gcc.json",
+    "problemMatcher": [
+        {
+            "owner": "v-problem-matcher",
+            "pattern": [
+                {
+                    "regexp": "^(.*):(\\d+):(\\d+):\\s+(?:fatal\\s+)?(warning|error|notice):\\s+(.*)$",
+                    "file": 1,
+                    "line": 2,
+                    "column": 3,
+                    "severity": 4,
+                    "message": 5
+                }
+            ]
+        }
+    ]
+}

GNUmakefile

@@ -118,6 +118,7 @@ endif
 	@$(VEXE) run cmd/tools/detect_tcc.v
 	@echo "V has been successfully built"
 	@$(VEXE) -version
+	@$(VEXE) run .github/problem-matchers/register_all.vsh
 
 clean:
 	rm -rf $(TMPTCC)

Makefile

@@ -15,8 +15,10 @@ v:
 	./v1 -no-parallel -o v2 $(VFLAGS) cmd/v
 	./v2 -o v $(VFLAGS) cmd/v
 	rm -rf v1 v2
-	@echo "V has been successfully built"
 	./v run ./cmd/tools/detect_tcc.v
+	@echo "V has been successfully built"
+	./v version
+	./v run .github/problem-matchers/register_all.vsh
 
 check:
 	./v test-all

make.bat

@@ -260,6 +260,7 @@ echo  ^> To add V to your PATH, run `%V_EXE% symlink`.
 echo.
 echo | set /p="V version: "
 "%V_EXE%" version
+"%V_EXE%" run .github/problem-matchers/register_all.vsh
 goto :eof
 
 :usage