fix: printf with -f at the beginning of a format string

fpistm · fpistm · commit bf0b3e39e1b4 · 2022-08-23T15:46:35.000+02:00
is recognized as an option

Signed-off-by: Frederic Pillon &lt;frederic.pillon@st.com&gt;
diff --git a/system/extras/prebuild.sh b/system/extras/prebuild.sh
@@ -14,7 +14,7 @@ fi
 # the board platform folder to a relative path by using '.'.
 # (i.e. the folder containing boards.txt)
 if [ ! -f "$BUILD_SOURCE_PATH/build_opt.h" ]; then
-  printf '-fmacro-prefix-map="%s"=.' "${BOARD_PLATFORM_PATH//\\/\\\\}" > "$BUILD_PATH/sketch/build.opt"
+  printf '\n-fmacro-prefix-map="%s"=.' "${BOARD_PLATFORM_PATH//\\/\\\\}" > "$BUILD_PATH/sketch/build.opt"
 else
   # Else copy the build_opt.h as build.opt
   # Workaround to the header file preprocessing done by arduino-cli
