deps: patch V8 to 6.1.534.38

Created using the update-v8 npm module and the command
`update-v8 minor`.

Refs: v8/v8@6.1.534.36...6.1.534.38

Backport-PR-URL: #15393
PR-URL: #15431
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

deps/v8/include/v8-version.h

@@ -11,7 +11,7 @@
 #define V8_MAJOR_VERSION 6
 #define V8_MINOR_VERSION 1
 #define V8_BUILD_NUMBER 534
-#define V8_PATCH_LEVEL 36
+#define V8_PATCH_LEVEL 38
 
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)

deps/v8/src/flag-definitions.h

@@ -491,7 +491,7 @@ DEFINE_BOOL(wasm_disable_structured_cloning, false,
             "disable wasm structured cloning")
 DEFINE_INT(wasm_num_compilation_tasks, 10,
            "number of parallel compilation tasks for wasm")
-DEFINE_BOOL(wasm_async_compilation, true,
+DEFINE_BOOL(wasm_async_compilation, false,
             "enable actual asynchronous compilation for WebAssembly.compile")
 // Parallel compilation confuses turbo_stats, force single threaded.
 DEFINE_VALUE_IMPLICATION(turbo_stats, wasm_num_compilation_tasks, 0)

deps/v8/src/libsampler/sampler.cc

@@ -450,11 +450,18 @@ void SignalHandler::FillRegisterState(void* context, RegisterState* state) {
   state->sp = reinterpret_cast<void*>(mcontext.gregs[29]);
   state->fp = reinterpret_cast<void*>(mcontext.gregs[30]);
 #elif V8_HOST_ARCH_PPC
+#if V8_LIBC_GLIBC
   state->pc = reinterpret_cast<void*>(ucontext->uc_mcontext.regs->nip);
   state->sp =
       reinterpret_cast<void*>(ucontext->uc_mcontext.regs->gpr[PT_R1]);
   state->fp =
       reinterpret_cast<void*>(ucontext->uc_mcontext.regs->gpr[PT_R31]);
+#else
+  // Some C libraries, notably Musl, define the regs member as a void pointer
+  state->pc = reinterpret_cast<void*>(ucontext->uc_mcontext.gp_regs[32]);
+  state->sp = reinterpret_cast<void*>(ucontext->uc_mcontext.gp_regs[1]);
+  state->fp = reinterpret_cast<void*>(ucontext->uc_mcontext.gp_regs[31]);
+#endif
 #elif V8_HOST_ARCH_S390
 #if V8_TARGET_ARCH_32_BIT
   // 31-bit target will have bit 0 (MSB) of the PSW set to denote addressing