Use full path for dirname and basename in osx_cc_wrapper.sh.tpl

Context: https://github.com/bazelbuild/rules_rust/pull/2998
diff --git a/cc/private/toolchain/osx_cc_wrapper.sh.tpl b/cc/private/toolchain/osx_cc_wrapper.sh.tpl
index e40a98b..4fbd546 100644
--- a/cc/private/toolchain/osx_cc_wrapper.sh.tpl
+++ b/cc/private/toolchain/osx_cc_wrapper.sh.tpl
@@ -113,9 +113,9 @@
 for rpath in ${RPATHS}; do
     for lib in ${LIBS}; do
         unset libname
-        if [ -f "$(dirname ${OUTPUT})/${rpath}/lib${lib}.so" ]; then
+        if [ -f "$(/usr/bin/dirname ${OUTPUT})/${rpath}/lib${lib}.so" ]; then
             libname="lib${lib}.so"
-        elif [ -f "$(dirname ${OUTPUT})/${rpath}/lib${lib}.dylib" ]; then
+        elif [ -f "$(/usr/bin/dirname ${OUTPUT})/${rpath}/lib${lib}.dylib" ]; then
             libname="lib${lib}.dylib"
         fi
         # ${libname-} --> return $libname if defined, or undefined otherwise. This is to make
@@ -129,8 +129,8 @@
     done
     for libpath in ${LIB_PATHS}; do
         if [ -f "$libpath" ]; then
-            libname=$(basename "$libpath")
-            if [ -f "$(dirname ${OUTPUT})/${rpath}/${libname}" ]; then
+            libname=$(/usr/bin/basename "$libpath")
+            if [ -f "$(/usr/bin/dirname ${OUTPUT})/${rpath}/${libname}" ]; then
                 call_install_name "${libpath}" "${rpath}" "${libname}"
             fi
         fi