Fail linking against -lstdc++ when building with `swift`

I am working on a Swift library that wraps LibRaw. I have libraw installed via homebrew and everything works great from Xcode. But when I try building my app / library from the CLI with swift I get a linker error:
ld: library not found for -lstdc++

I unterstand, that libstdc++ is deprecated on macOS and you should link against libc++. However, I wonder why the build works from within Xcode?

And what should be the correct fix? Should the hombrew formula for libraw patch the library to link against libc++ instead?

I can "fix" the problem by changing the libraw.pc file installed from homebrew to:

Libs: -L${libdir} -lraw -lstdc++ --> Libs: -L${libdir} -lraw -lc++

Maybe somebody knows how it should work and can share some insights :)

I am using the following module map for my libraw systemTarget:

module Clibraw [system] {
    umbrella header "Clibraw.h"
    link "raw"
    export *
}
// Clibraw.h:

#import <libraw/libraw.h>

Env:

swift --version
Apple Swift version 5.4.2 (swiftlang-1205.0.28.2 clang-1205.0.19.57)
Target: x86_64-apple-darwin20.6.0

Xcode: Version 12.5.1 (12E507)
macOS: 11.5.1 (20G80)