Update platform.txt

regex for sizes like in https://github.com/arduino/ArduinoCore-samd/blob/master/platform.txt#L120

Author: toxynoid

platform.txt

@@ -115,8 +115,8 @@ recipe.output.save_file_hexu={build.project_name}.save.hex
 
 ## Compute size
 recipe.size.pattern="{compiler.path}{compiler.size.cmd}" -A "{build.path}/{build.project_name}.elf"
-recipe.size.regex=^(\.text|.\data)\s+([0-9]+).*
-recipe.size.regex.data=^(\.data|\.bss)\s+([0-9]+).*
+recipe.size.regex=^(?:\.text|\.data|)\s+([0-9]+).*
+recipe.size.regex.data=^(?:\.data|\.bss)\s+([0-9]+).*
 
 ## Export Compiled Binary
 recipe.output.tmp_file={build.project_name}.hex