Motivation for this change

With the wrapper detection patch, if a build invokes an executable that cannot be found in PATH by find_executable, bear will fail with an AttributeError in os.path.realpath.

This can happen if the build invokes some project-local tool or command, like ./build-something.

Instead of calling using the result of find_executable directly, first check whether the executable was found and fall back to original Bear behavior if it was not.

The problem can be easily reproduced like this, for example:

cd /tmp \
    && mkdir -p test \
    && echo -e 'all:\n\t./command' > test/Makefile \
    && echo '#!/bin/sh\necho hello' > test/command \
    && chmod +x test/command \
    && bear make -C test

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.