NuttX build in place

- cmake NuttX build wrapper compile in place instead of copying source tree to build directory
    - slightly faster skipping necessary copying (depending on system)
    - allows debugging in place
    - easier to work directly in NuttX following official documentation
    - simplifies overall build which should make it easier to resolve any remaining NuttX dependency issues in the build system
 - the downside is switching back and forth between different builds always require rebuilding NuttX, but I think this is worth the improved developer experience
 - also no longer builds px4io and bootloader in every single build, for most users these rarely change and we're wasting a lot of build time

boards/av/x-v1/nuttx-config/nsh/defconfig

@@ -37,7 +37,7 @@
 # CONFIG_NSH_DISABLE_XD is not set
 CONFIG_ARCH="arm"
 CONFIG_ARCH_BOARD_CUSTOM=y
-CONFIG_ARCH_BOARD_CUSTOM_DIR="../nuttx-config"
+CONFIG_ARCH_BOARD_CUSTOM_DIR="../../../../boards/av/x-v1/nuttx-config"
 CONFIG_ARCH_BOARD_CUSTOM_DIR_RELPATH=y
 CONFIG_ARCH_BOARD_CUSTOM_NAME="px4"
 CONFIG_ARCH_CHIP="stm32f7"
@@ -123,7 +123,6 @@ CONFIG_NET_UDP=y
 CONFIG_NET_UDP_CHECKSUMS=y
 CONFIG_NET_UDP_WRITE_BUFFERS=y
 CONFIG_NSH_ARCHINIT=y
-CONFIG_NSH_ARCHROMFS=y
 CONFIG_NSH_ARGCAT=y
 CONFIG_NSH_BUILTIN_APPS=y
 CONFIG_NSH_CMDPARMS=y