Support pre- and post-build hooks correctly

[jscrane]

See the specification.

This is required for arduino-esp32 2.0.10.

`# 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.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}
recipe.hooks.core.prebuild.set_core_build_flag.pattern.windows=cmd /c echo "-DARDUINO_CORE_BUILD" > {file_opts.path}
recipe.hooks.core.postbuild.set_core_build_flag.pattern.windows=cmd /c type nul > {file_opts.path}
`

[jscrane]

Current status: have implemented prebuild and prelink hooks correctly. This is sufficient to support arduino-esp32 2.0.11.

The core.prebuild hook above isn't handled but this doesn't seem to matter.

Windows-override for these hooks isn't implemented.