t/lib/warnings/pp_sys: Add skips in case telldir is not available
lib/ExtUtils/t/Embed.t: Skip tests is cross-compiling and $Config{cc} is not available
dist/ExtUtils-Install: Skip tests if make is not available
Moved a glob test from t/run/fresh_perl.t to t/op/glob.t

This was done because, currently, the test fails when cross-compiling
perl, but run/fresh_perl.t can't use Config to check if we're cross-
compiling.
ext/DynaLoader/t/DynaLoader.t: Skip the dl_findfile test when cross-compiling
Add Darwin shared libraries (dylib) to gitignore
t/op/magic.t: Use three-arg open to avooid creating a subshell