fix(prebuild): made shell script fully posix

if called with other shell (example dash),
shebang is ignored and so some syntax was not supported.

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

system/extras/postbuild.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh -
 
 BUILD_PATH="$1"
 BUILD_SERIE="$2"

system/extras/prebuild.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh -
 
 BUILD_PATH="$1"
 BUILD_SOURCE_PATH="$2"
@@ -9,20 +9,38 @@ if [ ! -f "$BUILD_PATH/sketch" ]; then
   mkdir -p "$BUILD_PATH/sketch"
 fi
 
-# Create empty build.opt if build_opt.h does not exists in the original sketch dir
-# Then add or append -fmacro-prefix-map option to change __FILE__ absolute path of
-# the board platform folder to a relative path by using '.'.
-# (i.e. the folder containing boards.txt)
+# Create empty build.opt or clear it if build_opt.h does not exists in the original sketch dir
 if [ ! -f "$BUILD_SOURCE_PATH/build_opt.h" ]; then
-  printf '\n-fmacro-prefix-map="%s"=.' "${BOARD_PLATFORM_PATH//\\/\\\\}" > "$BUILD_PATH/sketch/build.opt"
+  true >"$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
   # See https://github.com/arduino/arduino-cli/issues/1338
-  cp "$BUILD_SOURCE_PATH/build_opt.h" "$BUILD_PATH/sketch/build.opt"
-  printf '\n-fmacro-prefix-map="%s"=.' "${BOARD_PLATFORM_PATH//\\/\\\\}" >> "$BUILD_PATH/sketch/build.opt"
+  cp -f "$BUILD_SOURCE_PATH/build_opt.h" "$BUILD_PATH/sketch/build.opt"
 fi
-
+# On Windows, need to protect '\' in path
+UNAME_OS="$(uname -s)"
+case "${UNAME_OS}" in
+  Windows*)
+    i=1
+    prefix=""
+    while [ "$i" -le "${#BOARD_PLATFORM_PATH}" ]; do
+      c=$(printf '%s' "$BOARD_PLATFORM_PATH" | cut -c $i)
+      prefix=${prefix}${c}
+      if [ "${c}" = "\\" ]; then
+        prefix=${prefix}"\\"
+      fi
+      i="$((i + 1))"
+    done
+    ;;
+  *)
+    prefix=${BOARD_PLATFORM_PATH}
+    ;;
+esac
+# Then append -fmacro-prefix-map option to change __FILE__ absolute path of
+# the board platform folder to a relative path by using '.'.
+# (i.e. the folder containing boards.txt)
+printf '\n-fmacro-prefix-map="%s"=.' "${prefix}" >>"$BUILD_PATH/sketch/build.opt"
 
 # Force include of SrcWrapper library
-echo "#include <SrcWrapper.h>" > "$BUILD_PATH/sketch/SrcWrapper.cpp"
+echo "#include <SrcWrapper.h>" >"$BUILD_PATH/sketch/SrcWrapper.cpp"