Add run_sk_stress_test script to run the stress tester over the source compatibility suite

The run_sk_stress_test script invokes runner.py passing sk-swiftc-wrapper to
--swiftc. This wrapper invokes swiftc, forwarding its own arguments, and if it
succeeds, additionally invokes sk-stress-test, which stress tests SourceKit on
all the .swift files in the passed compiler arguments.

As invoking swiftc and the stress tester takes significantly longer than swiftc
alone, the script tries to bring down the runtime without sacrificing too much
coverage by:

1. only running over the latest swift compatibilty version supported by each repo
2. only running over one of each set of platform-specific build actions (e.g.
   just RxSwift-macOS, rather than that + RxSwift-iOs, RxSift-tvOS, etc.)
3. only building generic/iOS actions for arm64, rather than arm64 and armv7

This patch also adds:
- an addition option to override the default timeout for common.check_execute()
  and related helper methods
- an optional 'tags' field on some actions that's used in combination with
  --include-acions to select the subset of actions to use in both a 'full'
  stress tester run, and the further reduced set for PR testing

Author: Nathan Hawes

.gitignore

@@ -14,3 +14,4 @@ swift-corelibs-foundation/
 swift-corelibs-libdispatch/
 swift-corelibs-xctest/
 swiftpm/
+swift-stress-tester/

cleanup

@@ -52,6 +52,7 @@ def main():
         'swift-corelibs-foundation',
         'swift-corelibs-libdispatch',
         'swift-corelibs-xctest',
+        'swift-stress-tester'
     ]
 
     if args.cleanup_cache:

common.py

@@ -143,6 +143,12 @@ def set_swift_branch(branch):
     swift_branch = branch
 
 
+def set_default_execute_timeout(timeout):
+    """Override the default execute timeout"""
+    global DEFAULT_EXECUTE_TIMEOUT
+    DEFAULT_EXECUTE_TIMEOUT = timeout
+
+
 def clone_repos():
     """Clone Swift and dependencies in parallel.
 
@@ -299,14 +305,16 @@ def __str__(self):
                     self.returncode))
 
 
-def execute(command, timeout=DEFAULT_EXECUTE_TIMEOUT,
+def execute(command, timeout=None,
             stdout=sys.stdout, stderr=sys.stderr,
             **kwargs):
     """Execute a given command with an optional timeout in seconds.
 
     >>> execute(['echo', 'Hello, World!'])
     0
     """
+    if timeout is None:
+        timeout = DEFAULT_EXECUTE_TIMEOUT
     shell_debug_print(command, stderr=stderr)
     returncode = 124  # timeout return code
     try:
@@ -320,13 +328,15 @@ def execute(command, timeout=DEFAULT_EXECUTE_TIMEOUT,
     return returncode
 
 
-def check_execute_output(command, timeout=DEFAULT_EXECUTE_TIMEOUT,
+def check_execute_output(command, timeout=None,
                          stdout=sys.stdout, stderr=sys.stderr, **kwargs):
     """Check execute a given command and return its output.
 
     >>> check_execute_output(['echo', 'Hello, World!'])
     'Hello, World!\\n'
     """
+    if timeout is None:
+        timeout = DEFAULT_EXECUTE_TIMEOUT
     shell_debug_print(command, stderr=stderr)
     try:
         with Timeout(timeout):
@@ -339,7 +349,7 @@ def check_execute_output(command, timeout=DEFAULT_EXECUTE_TIMEOUT,
     return output
 
 
-def check_execute(command, timeout=DEFAULT_EXECUTE_TIMEOUT,
+def check_execute(command, timeout=None,
                   sandbox_profile=None, max_retries=1,
                   stdout=sys.stdout, stderr=sys.stderr,
                   **kwargs):
@@ -348,6 +358,8 @@ def check_execute(command, timeout=DEFAULT_EXECUTE_TIMEOUT,
     >>> check_execute(['echo', 'Hello, World!'])
     0
     """
+    if timeout is None:
+        timeout = DEFAULT_EXECUTE_TIMEOUT
     if sandbox_profile:
         if platform.system() == 'Darwin':
             command = ['sandbox-exec', '-f', sandbox_profile] + command