fix(esp32c3): use semihosting _exit for QEMU emulator support

    Remove conflicting _exit implementations from libnosys and libgloss to
    ensure the semihosting version (from semihost-sys_exit.c, added as .o
    in #1537) is used for ESP32-C3 QEMU emulator.

    Changes:
    - Comment out libnosys/_exit.c
    - Comment out libgloss/riscv/sys_exit.c (3 occurrences)

    This allows proper exit handling in QEMU emulator via semihosting
    protocol instead of using the  instruction which causes crashes.

    Related: #1537

    🤖 Generated with [Claude Code](https://claude.com/claude-code)

    Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: luoliwoshang

internal/crosscompile/compile/libc/newlibesp.go

@@ -233,7 +233,6 @@ func getNewlibESP32ConfigRISCV(baseDir, target string) compile.CompileConfig {
 					filepath.Join(baseDir, "libgloss", "riscv", "sys_close.c"),
 					filepath.Join(baseDir, "libgloss", "riscv", "sys_conv_stat.c"),
 					filepath.Join(baseDir, "libgloss", "riscv", "sys_execve.c"),
-					filepath.Join(baseDir, "libgloss", "riscv", "sys_exit.c"),
 					filepath.Join(baseDir, "libgloss", "riscv", "sys_faccessat.c"),
 					filepath.Join(baseDir, "libgloss", "riscv", "sys_fork.c"),
 					filepath.Join(baseDir, "libgloss", "riscv", "sys_fstat.c"),
@@ -1112,7 +1111,6 @@ func getNewlibESP32ConfigXtensa(baseDir, target string) compile.CompileConfig {
 					filepath.Join(baseDir, "libgloss", "libnosys", "wait.c"),
 					filepath.Join(baseDir, "libgloss", "libnosys", "write.c"),
 					filepath.Join(baseDir, "libgloss", "libnosys", "getentropy.c"),
-					filepath.Join(baseDir, "libgloss", "libnosys", "_exit.c"),
 					filepath.Join(baseDir, "libgloss", "libnosys", "getreent.c"),
 					filepath.Join(baseDir, "libgloss", "libnosys", "time.c"),
 					filepath.Join(baseDir, "libgloss", "libnosys", "fcntl.c"),