There's a subtle difference in the internal name of siginfo_t fields
between glibc and musl. The structure itself is equivalent, so it
should suffice to add a macro to rename the field.

--- qtwebengine/src/3rdparty/chromium/sandbox/linux/seccomp-bpf/trap.cc	2015-02-17 05:57:43.000000000 +0100
+++ qtwebengine/src/3rdparty/chromium/sandbox/linux/seccomp-bpf/trap.cc	2015-06-03 08:20:25.032716427 +0200
@@ -22,6 +22,11 @@
 #include "sandbox/linux/services/android_ucontext.h"
 #endif

+// musl libc defines siginfo_t __si_fields instead of _sifields
+#if !defined(__GLIBC__)
+#define _sifields __si_fields
+#endif
+
 namespace {

 const int kCapacityIncrement = 20;