Resolve any symlinks to cwd in dylib install name

When the perl executable is installed by the installperl script, its
function `fix_dep_names` uses the perl function `getcwd` to determine
the current directory and uses it to change the path by which
libperl.dylib is referenced from the perl executable. `getcwd` resolves
symlinks.

At build time, the install name was set using a path constructed using
the shell command `pwd` which returns the current directory without
resolving symlinks.

This mismatch causes the executable to be installed with the wrong path
reference to the library in the case where the user has created a
symlink to the source directory and `cd`'d to that symlink rather than
to the real source directory. This was discovered while building perl in
MacPorts 2.11.2 which does exactly that.

See https://trac.macports.org/ticket/72715

Fix by using `pwd -P` instead which does resolve symlinks.

Author: ryandesign

Makefile.SH

@@ -64,7 +64,7 @@ true)
 				${revision}.${patchlevel}.${subversion}"
 		case "$osvers" in
 	        1[5-9]*|[2-9]*)
-			shrpldflags="$shrpldflags -install_name `pwd`/\$@ -Xlinker -headerpad_max_install_names"
+			shrpldflags="$shrpldflags -install_name `pwd -P`/\$@ -Xlinker -headerpad_max_install_names"
 			exeldflags="-Xlinker -headerpad_max_install_names"
 			;;
 		*)