fix(tst): resolve the temp directory in modulepath_test.sh (macOS)

Case 5 of the module-resolution suite failed on macOS only, because /var
is a symlink to /private/var there: `mktemp -d` returns an unresolved
path while Python's os.getcwd() reports the resolved one, so the test
compared two spellings of the same directory.  Resolving the temp
directory once at creation with `pwd -P` makes every path in the suite
consistent.

(from dev ca9eaa2c867a)

tst/modulepath_test.sh

@@ -31,7 +31,13 @@ green=$'\033[32m'
 bold=$'\033[1m'
 reset=$'\033[0m'
 
-T="$(mktemp -d)"
+# Resolve the temporary directory to its physical path.  On macOS /var is a
+# symlink to /private/var, so `mktemp -d` hands back an unresolved
+# /var/folders/... while Python's os.getcwd() reports the resolved
+# /private/var/folders/... — case 5 would then compare two spellings of the
+# same directory and fail on the Mac only.  `pwd -P` is POSIX; macOS has no
+# GNU realpath by default.
+T="$(cd "$(mktemp -d)" && pwd -P)"
 trap 'rm -rf "$T"' EXIT
 
 mkdir -p "$T/seta" "$T/setb" "$T/elsewhere"