Rework lit.cfg regex to avoid basename subshell in substituion

Changed %target-build-swift-dylib\(([^)]+)\) to
%target-build-swift-dylib\(([^)]+?)([^/()]+)\)

Group 1 now captures the "prefix" and group 2 captures the final word

Captured the basename directly in the regex instead of using a subshell since
Lit's internal shell does not support

Author: ramonasuncion

test/lit.cfg

@@ -1665,8 +1665,8 @@ if run_vendor == 'apple':
 
     config.target_build_swift_dylib = SubstituteCaptures(
         f"{escape_for_substitute_captures(config.target_build_swift)}"
-        r" -parse-as-library -emit-library -o '\1'"
-        r" -Xlinker -install_name -Xlinker @executable_path/$(basename '\1')"
+        r" -parse-as-library -emit-library -o '\1\2'"
+        r" -Xlinker -install_name -Xlinker @executable_path/\2"
     )
     config.target_add_rpath = SubstituteCaptures(r'-Xlinker -rpath -Xlinker \1')
 
@@ -2938,7 +2938,7 @@ config.substitutions.append(('%target-run-stdlib-swift', config.target_run_stdli
 config.substitutions.append(('%target-repl-run-simple-swift', subst_target_repl_run_simple_swift))
 config.substitutions.append(('%target-run', config.target_run))
 config.substitutions.append(('%target-jit-run', subst_target_jit_run))
-config.substitutions.append(('%target-build-swift-dylib\(([^)]+)\)', config.target_build_swift_dylib))
+config.substitutions.append(('%target-build-swift-dylib\(([^)]+?)([^/()]+)\)', config.target_build_swift_dylib))
 config.substitutions.append(('%target-codesign', config.target_codesign))
 config.substitutions.append(('%target-build-swift', config.target_build_swift))
 config.substitutions.append(('%target-clang', config.target_clang))