Fix Windows exports

[SergioGasquez]

• Windows export file now only contains \ instead of mixing / and \.
• GCC paths are now exported between " for Unix.

[SergioGasquez]

Please @georgik, can you verify that we solve #97 with this PR? You can use the Windows artifact achieved from the CI

[georgik]

@SergioGasquez Perfect. It works:

$Env:PATH += ";C:\Espressif\tools\xtensa-esp32s2-elf\esp-2021r2-patch5-8_4_0\xtensa-esp32s2-elf\bin"
$Env:PATH += ";C:\Espressif\tools\xtensa-esp32s3-elf\esp-2021r2-patch5-8_4_0\xtensa-esp32s3-elf\bin"
$Env:PATH += ";C:\Espressif\tools\xtensa-esp32-elf\esp-2021r2-patch5-8_4_0\xtensa-esp32-elf\bin"
$Env:PATH += ";C:\Espressif\tools\riscv32-esp-elf\esp-2021r2-patch5-8_4_0\riscv32-esp-elf\bin"
$Env:LIBCLANG_PATH="C:\Espressif\tools\xtensa-esp32-elf-clang\esp-15.0.0-20221201-x86_64-pc-windows-msvc\esp-clang\bin\libclang.dll"
$Env:PATH+=";C:\Espressif\tools\xtensa-esp32-elf-clang\esp-15.0.0-20221201-x86_64-pc-windows-msvc\esp-clang\bin"