Speed up processing of update-copyright.sh

(cherry picked from commit 78ccadd5a2)

build-scripts/update-copyright.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-find . -type f -exec grep -Il "Copyright" {} \; \
+find . -type f \
 | grep -v \.git                                 \
 | while read file; do                           \
     LC_ALL=C sed -b -i "s/\(.*Copyright.*\)[0-9]\{4\}\( *Sam Lantinga\)/\1`date +%Y`\2/" "$file"; \