When using FHSEnv in my project, cargo cant build ‘gdk-sys’ crate, because it dont see gdk-3.0.pc file, but it clearly specified and passed to PKG_CONFIG_PATH env variable.
shell.nix:

let
  ...
in
(pkgs.buildFHSEnv {
  name = "money_counter_dev";
  
  targetPkgs = pkgs: [
    rust
  ] ++ (with pkgs; [
    gcc
    pkg-config
    pkgsCross.mingwW64.stdenv.cc
  ]);

  profile = ''
    export RUST_BACKTRACE=1;
    export CARGO_TARGET_X86_64_PC_WINDOWS_GNU_RUSTFLAGS="-L native=${pkgs.pkgsCross.mingwW64.windows.pthreads}/lib";
    export PKG_CONFIG_PATH="${pkgs.gtk3.dev}/lib/pkgconfig:${pkgs.glib.dev}/lib/pkgconfig"
  '';
  

  runScript = ...
}).env

cargo check:

                                                                                           
  > PKG_CONFIG_PATH=/nix/store/m1v13sqd0h9qfvynrj20aqx17d5chkin-gtk+3-3.24.41-dev/lib/pkgconfig:/nix/store/gdr1ghkakyjfdj8bc6n0virwllm4zpwz-glib
-2.80.2-dev/lib/pkgconfig PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 pkg-config --libs --cflags gdk-3.0 gdk-3.0 >= 3.22                                   
                                                                                                                                                
  The system library `gdk-3.0` required by crate `gdk-sys` was not found.                                                                       
  The file `gdk-3.0.pc` needs to be installed and the PKG_CONFIG_PATH environment variable must contain its parent directory.                   
  PKG_CONFIG_PATH contains the following:                                                                                                       
      - /nix/store/m1v13sqd0h9qfvynrj20aqx17d5chkin-gtk+3-3.24.41-dev/lib/pkgconfig                                                             
      - /nix/store/gdr1ghkakyjfdj8bc6n0virwllm4zpwz-glib-2.80.2-dev/lib/pkgconfig                                                               
                                                                                                                                                
  HINT: you may need to install a package such as gdk-3.0, gdk-3.0-dev or gdk-3.0-devel.

contents of /nix/store/m1v13sqd0h9qfvynrj20aqx17d5chkin-gtk+3-3.24.41-dev/lib/pkgconfig

dr-xr-xr-x 1 nobody nogroup 318 Jan  1  1970 .
dr-xr-xr-x 1 nobody nogroup  18 Jan  1  1970 ..
-r--r--r-- 1 nobody nogroup 361 Jan  1  1970 gail-3.0.pc
-r--r--r-- 1 nobody nogroup 696 Jan  1  1970 gdk-3.0.pc
...

Expecting pkg-config to build required crate