texlab: fix cross-compilation

pkgs/development/tools/misc/texlab/default.nix

@@ -10,7 +10,9 @@
 , nix-update-script
 }:
 
-rustPlatform.buildRustPackage rec {
+let
+  isCross = stdenv.hostPlatform != stdenv.buildPlatform;
+in rustPlatform.buildRustPackage rec {
   pname = "texlab";
   version = "4.2.1";
 
@@ -23,12 +25,10 @@ rustPlatform.buildRustPackage rec {
 
   cargoSha256 = "sha256-wppaa3IGOqkFu/1CAp8g+PlPtMWm/7qNpPu0k4/mL3A=";
 
-  outputs = [ "out" "man" ];
+  outputs = [ "out" ] ++ lib.optional (!isCross) "man";
 
-  nativeBuildInputs = [
-    help2man
-    installShellFiles
-  ];
+  nativeBuildInputs = [ installShellFiles ]
+  ++ lib.optional (!isCross) help2man;
 
   buildInputs = lib.optionals stdenv.isDarwin [
     libiconv
@@ -37,17 +37,20 @@ rustPlatform.buildRustPackage rec {
   ];
 
   postInstall = ''
-    # TexLab builds man page separately in CI:
-    # https://github.com/latex-lsp/texlab/blob/v4.2.1/.github/workflows/publish.yml#L131-L135
-    help2man --no-info "$out/bin/texlab" > texlab.1
-    installManPage texlab.1
-
     # Remove generated dylib of human_name dependency. TexLab statically
     # links to the generated rlib and doesn't reference the dylib. I
     # couldn't find any way to prevent building this by passing cargo flags.
     # See https://github.com/djudd/human-name/blob/master/Cargo.toml#L43
     rm "$out/lib/libhuman_name${stdenv.hostPlatform.extensions.sharedLibrary}"
     rmdir "$out/lib"
+  ''
+  # When we cross compile we cannot run the output executable to
+  # generate the man page
+  + lib.optionalString (!isCross) ''
+    # TexLab builds man page separately in CI:
+    # https://github.com/latex-lsp/texlab/blob/v4.2.1/.github/workflows/publish.yml#L131-L135
+    help2man --no-info "$out/bin/texlab" > texlab.1
+    installManPage texlab.1
   '';
 
   passthru.updateScript = nix-update-script {