apps/cmake: Remove stale in-source builtin headers

[toku-mac]

apps/cmake: Remove stale in-source builtin headers

Summary

Remove stale in-source generated builtin headers during out-of-tree CMake builds.

Impact

• Impact on build: Prevents out-of-tree CMake builds from accidentally including stale apps/builtin/builtin_list.h and apps/builtin/builtin_proto.h generated by previous in-source or Make builds.

Testing

I confirm that changes are verified on local setup and works as intended:

• Build Host(s): OS (macOS 26.5), CPU(Apple M1), compiler(ARM GCC 14.3.rel1)
• Target(s): arch(thumbv8m)
• Ensure your PATH environment variable is properly configured to allow execution of: menuconfig, olddefconfig, savedefconfig, and setconfig.
• Use the Rust toolchain version prior to nightly-2026-04-29 to avoid errors related to lib/rustlib/src/rust/library/std/src/sys/net/connection/socket/unix.rs.

Configuration:

• First, set hello_rust_cargo to a valid state, then build it using make.

    Finished `dev` profile [unoptimized + debuginfo] target(s) in 19.72s
LN: platform/board to /Users/toku/nuttxspace/apps/platform/dummy
Register: hello_rust_cargo
Register: dd
Register: nsh
Register: sh
CPP:  /Users/toku/nuttxspace/nuttx/boards/arm/stm32h5/nucleo-h563zi/scripts/flash.ld-> /Users/toku/nuttxspace/nuLD: nuttx
arm-none-eabi-ld: warning: group_join.o: missing .note.GNU-stack section implies executable stack
arm-none-eabi-ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
Memory region         Used Size  Region Size  %age Used
           flash:     1266212 B         2 MB     60.38%
            sram:       11560 B       256 KB      4.41%
CP: nuttx.bin

• Assume the scenario where make distclean fails, leaving ~/apps/builtin/builtin_list.h and builtin_proto.h intact.
• Set the default configuration using cmake.

rm -rf build-default
cmake -S . -B build-default -DBOARD_CONFIG=nucleo-h563zi:nsh -GNinja
cmake --build build-default -t olddefconfig

Testing logs before change:

> cmake --build build-debug
...
-- Build files have been written to: /Users/toku/nuttxspace/nuttx/build-debug
[1149/1152] Linking CXX executable nuttx
FAILED: [code=1] nuttx
: && /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/arm-none-eabi-g++  --specs=nosys.specs -Wl,--print-memory-usage -Wl,--entry=__start -nostdlib -Wl,--gc-sections -Wl,--cref -Wl,-Map=nuttx.map @CMakeFiles/nuttx.rsp -o nuttx && :
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: apps/builtin/libapps_builtin.a(builtin_list.c.o):(.rodata.g_builtins+0x1c): undefined reference to `hello_rust_cargo_main'
Memory region         Used Size  Region Size  %age Used
           flash:      218876 B         2 MB     10.44%
            sram:        9808 B       256 KB      3.74%
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

Testing logs after change:

At cmake -S . -B build-default -DBOARD_CONFIG=nucleo-h563zi:nsh -GNinja stage, apps/builtin/builtin_list.h and apps/builtin/builtin_proto.h are removed.

-- Build files have been written to: /Users/toku/nuttxspace/nuttx/build-debug
[1149/1152] Linking CXX executable nuttx
Memory region         Used Size  Region Size  %age Used
           flash:      218848 B         2 MB     10.44%
            sram:        9808 B       256 KB      3.74%
[1151/1152] Generating System.map

PR verification Self-Check

• My PR adheres to Contributing Guidelines and Documentation (git commit title and message, coding standard, etc).
• My PR is ready for review and can be safely merged into a codebase.

[xuxin930]

In the nuttx/main CMakeLists generator phase, it actively checks for any remnants of make artifacts.

If any remnants of a previous make.config file are found, a fatal error will occur.

So, the assumption here is that only a portion of make distclean is cleaned up?

In that case, the problem to solve should be to perform a complete distclean.

[toku-mac]

I tried various methods to reproduce this state.

• Manual configuration changes via CLI commands
• Automatic processing of CMakeLists.txt by IDE

It seems there's an issue when running these simultaneously.
Following the proper workflow should prevent this problem, so I'll withdraw this pull request.

Thank you.