[build] Disable cleaning sourcekit-lsp by default, rather than having the flag do nothing

Rather than make this change, swiftlang/sourcekit-lsp@37d003eb7 had the
`--no-clean` flag do nothing, which means the flag can't be used at all.

Author: finagolfin

utils/swift_build_support/swift_build_support/products/indexstoredb.py

@@ -85,7 +85,7 @@ def get_dependencies(cls):
 
 
 def run_build_script_helper(action, host_target, product, args,
-                            sanitize_all=False, clean=True):
+                            sanitize_all=False, clean=False):
     script_path = os.path.join(
         product.source_dir, 'Utilities', 'build-script-helper.py')
 

utils/swift_build_support/swift_build_support/products/sourcekitlsp.py

@@ -54,14 +54,14 @@ def should_test(self, host_target):
     def test(self, host_target):
         indexstoredb.run_build_script_helper(
             'test', host_target, self, self.args,
-            self.args.test_sourcekitlsp_sanitize_all, clean=False)
+            self.args.test_sourcekitlsp_sanitize_all)
 
     def should_install(self, host_target):
         return self.args.install_sourcekitlsp
 
     def install(self, host_target):
         indexstoredb.run_build_script_helper(
-            'install', host_target, self, self.args, clean=False)
+            'install', host_target, self, self.args)
 
     @classmethod
     def get_dependencies(cls):