tools: fix config serialization w/ long strings

So that “config.gypi” gets serialized correctly in cases such as:

    ./configure --v8-options='--write-protect-code-memory \
    --wasm-write-protect-code-memory'

Where “v8_options” gets prettyprinted into a multiline string.

PR-URL: #35982
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

tools/js2c.py

@@ -163,9 +163,11 @@ def handle_config_gypi(config_filename):
 def jsonify(config):
   # 1. string comments
   config = re.sub(r'#.*?\n', '', config)
+  # 2. join multiline strings
+  config = re.sub(r"'$\s+'", '', config, flags=re.M)
   # 3. normalize string literals from ' into "
   config = re.sub('\'', '"', config)
-  # 2. turn pseudo-booleans strings into Booleans
+  # 4. turn pseudo-booleans strings into Booleans
   config = re.sub('"true"', 'true', config)
   config = re.sub('"false"', 'false', config)
   return config