cmake: fix make-clean as add_custom_command() deletes output files.

there is no way to mark output file as "precious", then cmake's
suggestion is to use add_custom_target() instead.

However that will always execute, so our generator script needs to be
smarter and only touch stuff when actually needed.

src/lib/ector/CMakeLists.txt

@@ -105,8 +105,7 @@ set(SOURCES
   software/ector_software_surface.c
 )
 
-add_custom_command(
-  OUTPUT ${EFL_LIB_SOURCE_DIR}/gl/shader/ector_gl_shaders.x
+add_custom_target(ector-update-shaders
   COMMAND /bin/sh ${EFL_LIB_SOURCE_DIR}/gl/shader/gen_shaders.sh
   DEPENDS
   ${EFL_LIB_SOURCE_DIR}/gl/shader/gen_shaders.sh
@@ -114,5 +113,7 @@ add_custom_command(
   ${EFL_LIB_SOURCE_DIR}/gl/shader/vertex.glsl
   ${EFL_LIB_SOURCE_DIR}/gl/shader/include.glsl
   WORKING_DIRECTORY "${EFL_LIB_SOURCE_DIR}"
-  COMMENT "SHADERS ${EFL_LIB_SOURCE_DIR}/gl/shader/ector_gl_shaders.x"
+  COMMENT "SHADERS src/lib/ector/gl/shader/ector_gl_shaders.x (if needed)"
 )
+
+set(DEPENDENCIES ector-update-shaders)

src/lib/ector/gl/shader/gen_shaders.sh

@@ -10,30 +10,43 @@ OUTPUT="$DIR/ector_gl_shaders.x"
 if ! git rev-parse 2>> /dev/null >> /dev/null ; then exit 0 ; fi
 if git diff --quiet --exit-code -- "$DIR"
 then
-  touch "$OUTPUT"
+  for f in gen_shaders.sh fragment.glsl vertex.glsl include.glsl; do
+    if [ "$DIR/$f" -nt "$OUTPUT" ]; then
+      touch "$OUTPUT"
+      break
+    fi
+  done
   exit 0
 fi
 
-exec 1<&-
-exec 1>"$OUTPUT"
-
 # Write header
-printf "/* DO NOT MODIFY THIS FILE AS IT IS AUTO-GENERATED */\n"
-printf "/* IF IT IS CHANGED PLEASE COMMIT THE CHANGES */\n\n"
+rm -f "$OUTPUT.tmp"
+cat <<EOF >> $OUTPUT.tmp
+/* DO NOT MODIFY THIS FILE AS IT IS AUTO-GENERATED */
+/* IF IT IS CHANGED PLEASE COMMIT THE CHANGES */
+
+EOF
 
 for SHD in fragment vertex ; do
   m4 "$DIR/include.glsl" "$DIR/$SHD.glsl" > "$SHD.tmp"
 
   OIFS="$IFS"
-  IFS=`printf '\n+'`
-  IFS=${IFS%+}
-  printf "static const char "$SHD"_glsl[] ="
+  IFS=$'\n'
+  echo -n "static const char ${SHD}_glsl[] =" >> "$OUTPUT.tmp"
   for LINE in `cat "$SHD.tmp"` ; do
-      printf "\n   \"$LINE\\\n\""
+      printf "\n   \"$LINE\\\n\"" >> "$OUTPUT.tmp"
   done
-  printf ";\n\n"
+  printf ";\n\n" >> "$OUTPUT.tmp"
   IFS="$OIFS"
 
   rm "$SHD.tmp"
 done
 
+if ! cmp "$OUTPUT" "$OUTPUT.tmp" >/dev/null 2>/dev/null; then
+    echo "$OUTPUT updated, please 'git commit' it."
+    rm -f "$OUTPUT"
+    mv "$OUTPUT.tmp" "$OUTPUT"
+else
+    rm -f "$OUTPUT.tmp"
+fi
+