fix(native): build on aarch64 with musl (#1665)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jpnurmi

CHANGELOG.md

@@ -14,6 +14,7 @@
 - Crashpad: build for 32-bit ARM on Linux. ([#1659](https://github.com/getsentry/sentry-native/issues/1659))
 - Native: build for 32-bit ARM on Linux. ([#1659](https://github.com/getsentry/sentry-native/issues/1659))
 - Inproc: build vendored libunwind for 32-bit ARM on Linux. ([#1659](https://github.com/getsentry/sentry-native/issues/1659))
+- Native: build for 64-bit ARM on Linux with musl. ([#1665](https://github.com/getsentry/sentry-native/pull/1665))
 - Native/Linux: prevent shared memory leak on crash. ([#1664](https://github.com/getsentry/sentry-native/pull/1664))
 
 ## 0.13.7

src/backends/native/minidump/sentry_minidump_linux.c

@@ -47,7 +47,8 @@ typedef struct {
 #        define FPSIMD_MAGIC 0x46508001
 
 // Only define these if not already provided by system headers
-#        ifndef __ASM_SIGCONTEXT_H
+// (on musl, defined in <bits/signal.h> instead).
+#        if !defined(__ASM_SIGCONTEXT_H) && defined(__GLIBC__)
 // Base header for context blocks in __reserved
 struct _aarch64_ctx {
     uint32_t magic;