pcre: fix hardwired reference to /usr/bin/file in configure

[ghost]

The configure script that ships with pcre expects to be able to use
"file", via the hardwired path "/usr/bin/file". When cross-compiling
in a sandboxed build this will cause it to mis-detect the ability to
create shared libraries.

Let's fix this, and perform the substitution only for cross compiles,
in order to avoid a mass-rebuild.

Currently this problem is preventing Hydra from generating the
bootstrap tarball for mips64el-linux-gnuabi64.

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux
  • mips64-linux-gnuabi64, cross from x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.05 Release Notes (or backporting 21.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

The configure script that ships with pcre expects to be able to use
"file", via the hardwired path "/usr/bin/file". When cross-compiling
in a sandboxed build this will cause it to mis-detect the ability to
create shared libraries.

Let's fix this, and perform the substitution only for cross compiles,
in order to avoid a mass-rebuild.

Currently this problem is preventing Hydra from generating the
bootstrap tarball for mips64el-linux-gnuabi64.

[ghost]

The failure which occurs without this commit can be found here:

./configure: line 9843: /usr/bin/file: No such file or directory
./configure: line 9851: /usr/bin/file: No such file or directory
./configure: line 9859: /usr/bin/file: No such file or directory

leading to:

checking whether to build shared libraries... no

[ghost]

@ofborg build pkgsCross.mips64el-linux-gnuabi64.pcre

[ghost]

Yep, it built:

shrinking /nix/store/7ggx4sdpad6smyq9rmrr141q571sxkz2-pcre-mips64el-linux-gnuabi64-8.45/lib/libpcre.so.1.2.13

[ghost]

@ofborg build this-is-a-kludge

[ghost]

The problem appears to come from the code below. Apparently when cross-compiling to some platforms, autoconf uses file to figure out certain things about the host platform.

mips64*-*linux*)
  # Find out what ABI is being produced by ac_compile, and set linker
  # options accordingly.
...
  test $ac_status = 0; }; then
    emul=elf
    case `/usr/bin/file conftest.$ac_objext` in

It does this for most linux-kernel host platforms, including x86_64, mips64el, sparc, and powerpc, but not for aarch64, which is probably why we haven't noticed it before.

[ghost]

Ugh, the same problem happens elsewhere.

I need to fix this at the source, in libtool.