conf-libev.4-12 - Misleading error message on arch mismatch

[exlee]

Hi!

I was trying to install conf-libev.4-12, but started getting:

testing for libev: ............................. unavailable

      The following recquired C libraries are missing: libev.
Please install them and retry. If they are installed in a non-standard location, set the environment variables C_INCLUDE_PATH and LIBRARY_PATH accordingly and retry.

For example, if they are installed in /opt/local, you can type:

export C_INCLUDE_PATH=/opt/local/include
export LIBRARY_PATH=/opt/local/lib

To compile without libev support, use ./configure --disable-libev ...

...which sent me for a goose hunt on trying to get libev installed. After confirming all files are correct I decided to debug the package itself and found that build failed with following message.

clang: warning: argument unused during compilation: '-L/opt/local/lib' [-Wunused-command-line-argument]
clang: warning: argument unused during compilation: '-L/opt/local/lib' [-Wunused-command-line-argument]
ld: warning: ignoring file '/opt/local/lib/libev.4.dylib': found architecture 'arm64', required architecture 'x86_64'
Undefined symbols for architecture x86_64:
  "_ev_default_loop", referenced from:
      _lwt_test in lwt_stub236629.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
File "/var/folders/gg/g9217_cs7t1b1zxqbb21v4fc0000gn/T/lwt_caml1c071d.ml", line 1:

discover.ml for conf-libenv is pulled from the archive, so I'm not sure how I to submit PR but I think that spitting out compilation error would be enough (I was somewhat surprised that I'm running x86_64 on arm64).