With latest swift master you can use the build-parser-lib script to build the parser library for iOS:
utils/build-parser-lib --release --no-assertions --build-dir /tmp/parser-lib-build-ios --host iphoneos --architectures arm64
or
utils/build-parser-lib --release --no-assertions --build-dir /tmp/parser-lib-build-iossim --host iphonesimulator --architectures x86_64