Bug 1949205 - Create artifacts directory if it doesn't exist. r=perftest-reviewers,afinder

This patch ensures that the artifacts directory gets created if it doesn't exist when running mach perftest locally. It also adds a check for the existence of the output directory during mochitest gecko profiling. At the same time, the aritfacts folder is added to the hg/git ignore files.

Differential Revision: https://phabricator.services.mozilla.com/D238791

.gitignore

@@ -359,3 +359,6 @@ media/libvpx/config/**/config.log
 
 # Ignore generated files resulting from building the minidump analyzer tests.
 toolkit/crashreporter/minidump-analyzer/analyzer-test/target/
+
+# Ignore mozperftest artifacts folder
+/artifacts/

.hgignore

@@ -359,3 +359,6 @@ toolkit/themes/shared/design-system/node_modules/
 
 # Ignore generated files resulting from building the minidump analyzer tests.
 ^toolkit/crashreporter/minidump-analyzer/analyzer-test/target/
+
+# Ignore mozperftest artifacts folder
+^artifacts/

python/mozperftest/mozperftest/mach_commands.py

@@ -3,6 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 import json
 import os
+import pathlib
 import sys
 from functools import partial
 
@@ -88,6 +89,10 @@ def run_perftest(command_context, **kwargs):
         print("\nSorry no support yet for multiple local perftest")
         return
 
+    # Make sure the default artifacts directory exists
+    default_artifact_location = pathlib.Path(command_context.topsrcdir, "artifacts")
+    default_artifact_location.mkdir(parents=True, exist_ok=True)
+
     sel = "\n".join(kwargs["tests"])
     print("\nGood job! Best selection.\n%s" % sel)
     # if the script is xpcshell, we can force the flavor here

python/mozperftest/mozperftest/test/mochitest.py

@@ -156,9 +156,11 @@ class Mochitest(Layer):
                 # Setup where the profile gets saved to so it doesn't get deleted
                 profile_path = os.getenv("MOZ_PROFILER_SHUTDOWN")
                 if not profile_path:
-                    profile_path = (
+                    output_dir = Path(self.get_arg("output"))
-                        Path(self.get_arg("output")) / "profile_mochitest.json"
+                    if not output_dir.is_absolute():
-                    )
+                        output_dir = Path(self.topsrcdir, output_dir)
+                    output_dir.resolve().mkdir(parents=True, exist_ok=True)
+                    profile_path = output_dir / "profile_mochitest.json"
                     os.environ["MOZ_PROFILER_SHUTDOWN"] = str(profile_path)
                 self.info(f"Profile will be saved to: {profile_path}")