mtrace: init at 2.33-50

`mtrace(1)` is a small Perl script that interprets and provides
human-readable output for `malloc(3)` traces.

Even though this is actually part of `glibc` itself I decided to place
this into its own package. The main reason for this is that this script
has a runtime dependency on Perl which would complicate `stdenv`
bootstrapping since we'd have to compile another Perl that doesn't depend on
the bootstrap tools that is used as runtime dependency for the
stage2 glibc.

Since this is only a dev/debugging tool, splitting this up seemed like a
reasonable choice to me.

On a leaking C program, this can be used like this:

$ env MALLOC_TRACE=$(pwd)/trace ./a.out
$ ./result/bin/mtrace ./trace

Memory not freed:
-----------------
Address Size Caller
0x0000000001875690 0x4 at 0x401151

Closes #141924

pkgs/development/libraries/glibc/common.nix

···
   BASH_SHELL = "/bin/sh";
 
   # Used by libgcc, elf-header, and others to determine ABI
-  passthru = { inherit version; };
+  passthru = { inherit version; minorRelease = version; };
 }
 
 // (removeAttrs args [ "withLinuxHeaders" "withGd" ]) //

pkgs/development/libraries/glibc/mtrace.nix

···
+{ glibc, perl }:
+
+# Small wrapper which only exposes `mtrace(3)` from `glibc`. This can't be placed
+# into `glibc` itself because it depends on Perl which would mean that the final
+# `glibc` inside a stdenv bootstrap has a dependency `glibc -> perl -> bootstrap tools`,
+# so this is now in its own package that isn't used for bootstrapping.
+#
+# `glibc` needs to be overridden here because it's still needed to `./configure` the source in order
+# to have a build environment where we can call the needed make target.
+
+glibc.overrideAttrs ({ meta ? {}, ... }: {
+  pname = "glibc-mtrace";
+
+  buildPhase = ''
+    runHook preBuild
+
+    mkdir malloc
+    make -C ../glibc-${glibc.minorRelease}/malloc objdir=`pwd` `pwd`/malloc/mtrace;
+
+    runHook postBuild
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin
+    mv malloc/mtrace $out/bin/
+  '';
+
+  # Perl interpreter used for `mtrace`.
+  buildInputs = [ perl ];
+
+  # Reset a few things declared by `pkgs.glibc`.
+  outputs = [ "out" ];
+  separateDebugInfo = false;
+
+  meta = meta // {
+    description = "Perl script used to interpret and provide human readable output of the trace log contained in the file mtracedata, whose contents were produced by mtrace(3).";
+  };
+})

pkgs/top-level/all-packages.nix

···
     stdenv = gccStdenv; # doesn't compile without gcc
   };
 
+  mtrace = callPackage ../development/libraries/glibc/mtrace.nix { };
+
   # Provided by libc on Operating Systems that use the Extensible Linker Format.
   elf-header =
     if stdenv.hostPlatform.parsed.kernel.execFormat.name == "elf"