From b69e2e84e06f40b9ead2019e20e6ace673feca01 Mon Sep 17 00:00:00 2001
From: David McFarland <corngood@gmail.com>
Date: Wed, 16 Oct 2024 10:50:33 -0300
Subject: [PATCH 1/2] jam: add test for OS=UNKNOWN

---
 pkgs/by-name/ja/jam/package.nix | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/pkgs/by-name/ja/jam/package.nix b/pkgs/by-name/ja/jam/package.nix
index 584617180db6..65b02a15076b 100644
--- a/pkgs/by-name/ja/jam/package.nix
+++ b/pkgs/by-name/ja/jam/package.nix
@@ -87,6 +87,15 @@ stdenv.mkDerivation (finalAttrs: {
       package = finalAttrs.finalPackage;
       command = "jam -v";
     };
+    tests.os = testers.runCommand {
+      name = "${finalAttrs.finalPackage.name}-os";
+      nativeBuildInputs = [ finalAttrs.finalPackage ];
+      script = ''
+        echo 'echo $(OS) ;' > Jamfile
+        os=$(jam -d0)
+        [[ $os != UNKNOWN* ]] && touch $out
+      '';
+    };
   };
 
   meta = {

From 59ede8c22324289fd812bc10274c4b47b64fd727 Mon Sep 17 00:00:00 2001
From: David McFarland <corngood@gmail.com>
Date: Wed, 16 Oct 2024 10:50:13 -0300
Subject: [PATCH 2/2] jam: fix OS determination on linux

---
 pkgs/by-name/ja/jam/package.nix | 35 +++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/pkgs/by-name/ja/jam/package.nix b/pkgs/by-name/ja/jam/package.nix
index 65b02a15076b..9fbe6f4c7724 100644
--- a/pkgs/by-name/ja/jam/package.nix
+++ b/pkgs/by-name/ja/jam/package.nix
@@ -49,21 +49,26 @@ stdenv.mkDerivation (finalAttrs: {
     export AR="$AR rc"
   '';
 
-  # When cross-compiling, we need to set the preprocessor macros
-  # OSMAJOR/OSMINOR/OSPLAT to the values from the target platform, not the host
-  # platform. This looks a little ridiculous because the vast majority of build
-  # tools don't embed target-specific information into their binary, but in this
-  # case we behave more like a compiler than a make(1)-alike.
-  postPatch = lib.optionalString (stdenv.hostPlatform != stdenv.targetPlatform) ''
-     cat >>jam.h <<EOF
-     #undef OSMAJOR
-     #undef OSMINOR
-     #undef OSPLAT
-     $(
-       ${pkgsBuildTarget.targetPackages.stdenv.cc}/bin/${pkgsBuildTarget.targetPackages.stdenv.cc.targetPrefix}cc -E -dM jam.h | grep -E '^#define (OSMAJOR|OSMINOR|OSPLAT) '
-      )
-    EOF
-  '';
+  postPatch =
+    ''
+      substituteInPlace jam.h --replace-fail 'ifdef linux' 'ifdef __linux__'
+    ''
+    +
+      # When cross-compiling, we need to set the preprocessor macros
+      # OSMAJOR/OSMINOR/OSPLAT to the values from the target platform, not the host
+      # platform. This looks a little ridiculous because the vast majority of build
+      # tools don't embed target-specific information into their binary, but in this
+      # case we behave more like a compiler than a make(1)-alike.
+      lib.optionalString (stdenv.hostPlatform != stdenv.targetPlatform) ''
+         cat >>jam.h <<EOF
+         #undef OSMAJOR
+         #undef OSMINOR
+         #undef OSPLAT
+         $(
+           ${pkgsBuildTarget.targetPackages.stdenv.cc}/bin/${pkgsBuildTarget.targetPackages.stdenv.cc.targetPrefix}cc -E -dM jam.h | grep -E '^#define (OSMAJOR|OSMINOR|OSPLAT) '
+          )
+        EOF
+      '';
 
   buildPhase = ''
     runHook preBuild