texinfo: fix build references when cross-compiling

The XS modules were being built for the build platform, and the perl scripts
had build platform shebangs.

It is possible to build the XS modules by passing
PERL_EXT_CC=${stdenv.cc.targetPrefix}cc and --enable-perl-xs=yes, but they
fail to load due to a handshake key mismatch. Instead, I just decided to
disable the XS modules and use the pure Perl fallbacks when cross-compiling.

The shebangs were fixed manually using substituteInPlace.

pkgs/development/tools/misc/texinfo/common.nix

@@ -36,8 +36,7 @@ stdenv.mkDerivation {
   strictDeps = true;
   enableParallelBuilding = true;
 
-  # We need a native compiler to build perl XS extensions
-  # when cross-compiling.
+  # A native compiler is needed to build tools needed at build time
   depsBuildBuild = [ buildPackages.stdenv.cc perl ];
 
   buildInputs = [ xz.bin bash libintl ]
@@ -45,6 +44,9 @@ stdenv.mkDerivation {
     ++ optional interactive ncurses;
 
   configureFlags = [ "PERL=${buildPackages.perl}/bin/perl" ]
+    # Perl XS modules are difficult to cross-compile and texinfo has pure Perl
+    # fallbacks.
+    ++ optional crossBuildTools "--enable-perl-xs=no"
     ++ lib.optional stdenv.isSunOS "AWK=${gawk}/bin/awk";
 
   installFlags = [ "TEXMF=$(out)/texmf-dist" ];
@@ -62,6 +64,13 @@ stdenv.mkDerivation {
     "XFAIL_TESTS=test_scripts/layout_formatting_fr_icons.sh"
   ];
 
+  postFixup = optionalString crossBuildTools ''
+    for f in "$out"/bin/{pod2texi,texi2any}; do
+      substituteInPlace "$f" \
+        --replace ${buildPackages.perl}/bin/perl ${perl}/bin/perl
+    done
+  '';
+
   meta = {
     homepage = "https://www.gnu.org/software/texinfo/";
     description = "The GNU documentation system";