Fix unexpected EOF (#8424)

Author: pennam

platform.txt

@@ -189,7 +189,7 @@ recipe.hooks.prebuild.6.pattern.windows=cmd /c if not exist "{build.path}\build_
 # Set -DARDUINO_CORE_BUILD only on core file compilation
 file_opts.path={build.path}/file_opts
 recipe.hooks.prebuild.set_core_build_flag.pattern=bash -c ": > {file_opts.path}"
-recipe.hooks.core.prebuild.set_core_build_flag.pattern=bash -c "echo '-DARDUINO_CORE_BUILD' > {file_opts.path}"
+recipe.hooks.core.prebuild.set_core_build_flag.pattern=bash -c "echo -DARDUINO_CORE_BUILD > {file_opts.path}"
 recipe.hooks.core.postbuild.set_core_build_flag.pattern=bash -c ": > {file_opts.path}"
 
 recipe.hooks.prebuild.set_core_build_flag.pattern.windows=cmd /c type nul > {file_opts.path}