Specify path to sed on MacOS and FreeBSD (#961)

Co-authored-by: James Sharpe <james.sharpe@zenotech.com>

foreign_cc/private/framework/toolchains/freebsd_commands.bzl

@@ -83,7 +83,7 @@ if [ -d "$1" ]; then
   for file in ${files[@]+"${files[@]}"}; do
     local backup=$(mktemp)
     touch -r "${file}" "${backup}"
-    sed -i '' -e 's@'"$2"'@'"$3"'@g' "${file}"
+    /usr/bin/sed -i '' -e 's@'"$2"'@'"$3"'@g' "${file}"
     if [[ "$?" -ne "0" ]]; then
       exit 1
     fi

foreign_cc/private/framework/toolchains/macos_commands.bzl

@@ -74,7 +74,7 @@ if [ -d "$1" ]; then
   for file in ${files[@]+"${files[@]}"}; do
     local backup=$(mktemp)
     touch -r "${file}" "${backup}"
-    sed -i '' -e 's@'"$2"'@'"$3"'@g' "${file}"
+    /usr/bin/sed -i '' -e 's@'"$2"'@'"$3"'@g' "${file}"
     if [[ "$?" -ne "0" ]]; then
       exit 1
     fi