ninjabackend: prefer "in" to regex search

Regexes can be surprisingly slow.  This small change brings
ninja_quote() from 12 to 3 seconds when building QEMU.
Before:

   ncalls  tottime  percall  cumtime  percall
  3734443    4.872    0.000   11.944    0.000

After:

   ncalls  tottime  percall  cumtime  percall
  3595590    3.193    0.000    3.196    0.000

Signed-off-by: Paolo Bonzini <[email protected]>

mesonbuild/backend/ninjabackend.py

@@ -123,21 +123,26 @@ def get_rsp_threshold() -> int:
 NINJA_QUOTE_VAR_PAT = re.compile(r"[$ \n]")
 
 def ninja_quote(text: str, is_build_line: bool = False) -> str:
-    if is_build_line:
-        quote_re = NINJA_QUOTE_BUILD_PAT
-    else:
-        quote_re = NINJA_QUOTE_VAR_PAT
-    # Fast path for when no quoting is necessary
-    if not quote_re.search(text):
-        return text
     if '\n' in text:
         errmsg = f'''Ninja does not support newlines in rules. The content was:
 
 {text}
 
 Please report this error with a test case to the Meson bug tracker.'''
         raise MesonException(errmsg)
-    return quote_re.sub(r'$\g<0>', text)
+
+    if is_build_line:
+        if ':' in text:
+            return NINJA_QUOTE_BUILD_PAT.sub(r'$\g<0>', text)
+        quote_re = NINJA_QUOTE_BUILD_PAT
+    else:
+        quote_re = NINJA_QUOTE_VAR_PAT
+
+    if ' ' in text:
+        return quote_re.sub(r'$\g<0>', text)
+    if '$' in text:
+        return quote_re.sub(r'$\g<0>', text)
+    return text
 
 
 @dataclass