cpython: fix _PYTHON_SYSCONFIGDATA_NAME on armv7l with musl (#240770)

Python always uses "gnu" prefixed ABI names, and this patch handles this by
doing a musl->gnu string replacement.

With pkgsCross.armv7l-hf-multiplatform.pkgsStatic, the previous name was:
_sysconfigdata__linux_arm-linux-gnu
Now, the corrected name is:
_sysconfigdata__linux_arm-linux-gnueabihf

pkgs/development/interpreters/python/cpython/default.nix

···
         if parsed.cpu.significantByte.name == "littleEndian" then "arm" else "armeb"
       else if isx86_32 then "i386"
       else parsed.cpu.name;
+    # Python doesn't distinguish musl and glibc and always prefixes with "gnu"
+    gnuAbiName = replaceStrings [ "musl" ] [ "gnu" ] parsed.abi.name;
     pythonAbiName =
       # python's build doesn't support every gnu<extension>, and doesn't
       # differentiate between musl and glibc, so we list those supported in
···
       # https://github.com/python/cpython/blob/e488e300f5c01289c10906c2e53a8e43d6de32d8/configure.ac#L724
       # Note: this is an approximation, as it doesn't take into account the CPU
       # family, or the nixpkgs abi naming conventions.
-      if elem parsed.abi.name [
+      if elem gnuAbiName [
         "gnux32"
         "gnueabihf"
         "gnueabi"
···
         "gnuabi64"
         "gnuspe"
       ]
-      then parsed.abi.name
+      then gnuAbiName
       else "gnu";
     multiarch =
       if isDarwin then "darwin"