[lit] Add %:[STpst] to represent paths without Windows drive letters.

[ruiu]

Summary

We need these variables to concatenate two absolute paths to construct
a valid path. Currently, %t/%t is, for example, expanded to C:/foo/C:/foo,
which is not a valid path because ":" is not a valid path character
on Windows.

[rnk]

I thought we wanted this behavior:

C:/foo -> C/foo

Is LLD doing something different in the reproducer?

[ruiu]

• Update as per Reid's comment.

[• rafael]

LGTM

[ruiu]

I don't think UNC names (paths start with \\) have colons in them, so we don't need to remove anything from UNC names.

utils/lit/lit/TestRunner.py

def getDefaultSubstitutions(test, tmpDir, tmpBase, normalize_slashes=False):
     # "%/[STpst]" should be normalized.
     substitutions.extend([
             ('%/s', sourcepath.replace('\\', '/')),
             ('%/S', sourcedir.replace('\\', '/')),
             ('%/p', sourcedir.replace('\\', '/')),
             ('%/t', tmpBase.replace('\\', '/') + '.tmp'),
             ('%/T', tmpDir.replace('\\', '/')),
             ])
+
+    # "%:[STpst]" are paths without Windows drive letters.
+    if kIsWindows:
+        substitutions.extend([
+                ('%:s', re.sub(r'^.:', '', sourcepath)),
+                ('%:S', re.sub(r'^.:', '', sourcedir)),
+                ('%:p', re.sub(r'^.:', '', sourcedir)),
+                ('%:t', re.sub(r'^.:', '', tmpBase) + '.tmp'),
+                ('%:T', re.sub(r'^.:', '', tmpDir)),
+                ])
+    else:
+        substitutions.extend([
+                ('%:s', sourcepath),
+                ('%:S', sourcedir),
+                ('%:p', sourcedir),
+                ('%:t', tmpBase + '.tmp'),
+                ('%:T', tmpDir),
+                ])
     return substitutions
 
 def applySubstitutions(script, substitutions):
     """Apply substitutions to the script.  Allow full regular expression syntax.
     Replace each matching occurrence of regular expression pattern a with
     substitution b in line ln."""
     def processLine(ln):
         # Apply substitutions