brp-mangle-shebangs: speed up finding of "text executables" (scripts)

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

brp-mangle-shebangs

@@ -74,9 +74,17 @@ trim() {
   printf '%s' "$*"
 }
 
+# Large packages such as kernel can have thousands of executable files.
+# We take care to not fork/exec thousands of "file"s and "grep"s,
+# but run just two of them.
+# (Take care to exclude filenames which would mangle "file" output).
+find -executable -type f ! -path '*:*' ! -path $'*\n*' \
+| file -N --mime-type -f - \
+| grep -P ".+(?=: text/)" \
+| {
 fail=0
-while IFS= read -r -d $'\0' f; do
-  file -N --mime-type "$f" | grep -q -P ".+(?=: text/)" || continue
+while IFS= read -r line; do
+  f=${line%%:*}
 
   # Remove the dot
   path="${f#.}"
@@ -137,6 +145,7 @@ while IFS= read -r -d $'\0' f; do
   fi
 
   touch -d "$ts" "$f"
-done < <(find -executable -type f -print0)
+done
 
 exit $fail
+}