Diff below makes it build on arm64. Not sure of it actually works.
ok?
Index: www/webkitgtk4/patches/patch-Source_JavaScriptCore_offlineasm_arm64_rb
===================================================================
RCS file: www/webkitgtk4/patches/patch-Source_JavaScriptCore_offlineasm_arm64_rb
diff -N www/webkitgtk4/patches/patch-Source_JavaScriptCore_offlineasm_arm64_rb
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ www/webkitgtk4/patches/patch-Source_JavaScriptCore_offlineasm_arm64_rb
16 May 2018 20:19:01 -0000
@@ -0,0 +1,14 @@
+$OpenBSD$
+
+Index: Source/JavaScriptCore/offlineasm/arm64.rb
+--- Source/JavaScriptCore/offlineasm/arm64.rb.orig
++++ Source/JavaScriptCore/offlineasm/arm64.rb
+@@ -945,7 +945,7 @@ class Instruction
+ $asm.puts "ldr #{operands[1].arm64Operand(:ptr)},
[#{operands[1].arm64Operand(:ptr)}, #{operands[0].asmLabel}@GOTPAGEOFF]"
+
+ # On Linux, use ELF GOT relocation specifiers.
+- $asm.putStr("#elif OS(LINUX)")
++ $asm.putStr("#elif OS(LINUX) || OS(OPENBSD)")
+ $asm.puts "adrp #{operands[1].arm64Operand(:ptr)},
:got:#{operands[0].asmLabel}"
+ $asm.puts "ldr #{operands[1].arm64Operand(:ptr)},
[#{operands[1].arm64Operand(:ptr)}, :got_lo12:#{operands[0].asmLabel}]"
+
Index:
www/webkitgtk4/patches/patch-Source_JavaScriptCore_runtime_MachineContext_h
===================================================================
RCS file:
/cvs/ports/www/webkitgtk4/patches/patch-Source_JavaScriptCore_runtime_MachineContext_h,v
retrieving revision 1.2
diff -u -p -r1.2 patch-Source_JavaScriptCore_runtime_MachineContext_h
--- www/webkitgtk4/patches/patch-Source_JavaScriptCore_runtime_MachineContext_h
19 Mar 2018 08:13:15 -0000 1.2
+++ www/webkitgtk4/patches/patch-Source_JavaScriptCore_runtime_MachineContext_h
16 May 2018 20:19:01 -0000
@@ -16,7 +16,7 @@ Index: Source/JavaScriptCore/runtime/Mac
+#elif CPU(ARM)
+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.__gregs[_REG_SP]);
+#elif CPU(ARM64)
-+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.mc_gpregs.gp_sp);
++ return reinterpret_cast<void*&>((uintptr_t&) machineContext.sc_sp);
+#elif CPU(MIPS)
+ return reinterpret_cast<void*&>((uintptr_t&) machineContext.mc_regs[29]);
+#elif CPU(SPARC64)
@@ -41,7 +41,7 @@ Index: Source/JavaScriptCore/runtime/Mac
+#elif CPU(ARM)
+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.__gregs[_REG_FP]);
+#elif CPU(ARM64)
-+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.mc_gpregs.gp_x[29]);
++ return reinterpret_cast<void*&>((uintptr_t&) machineContext.sc_x[29]);
+#elif CPU(MIPS)
+ return reinterpret_cast<void*&>((uintptr_t&) machineContext.mc_regs[30]);
+#elif CPU(SPARC64)
@@ -66,7 +66,7 @@ Index: Source/JavaScriptCore/runtime/Mac
+#elif CPU(ARM)
+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.__gregs[_REG_PC]);
+#elif CPU(ARM64)
-+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.mc_gpregs.gp_elr);
++ return reinterpret_cast<void*&>((uintptr_t&) machineContext.sc_elr);
+#elif CPU(MIPS)
+ return reinterpret_cast<void*&>((uintptr_t&) machineContext.mc_pc);
+#elif CPU(SPARC64)
@@ -91,7 +91,7 @@ Index: Source/JavaScriptCore/runtime/Mac
+#elif CPU(ARM)
+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.__gregs[_REG_R1]);
+#elif CPU(ARM64)
-+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.mc_gpregs.gp_x[1]);
++ return reinterpret_cast<void*&>((uintptr_t&) machineContext.sc_x[1]);
+#elif CPU(MIPS)
+ return reinterpret_cast<void*&>((uintptr_t&) machineContext.mc_regs[5]);
+#elif CPU(SPARC64)
@@ -120,7 +120,7 @@ Index: Source/JavaScriptCore/runtime/Mac
+#elif CPU(ARM)
+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.__gregs[_REG_R8]);
+#elif CPU(ARM64)
-+ return reinterpret_cast<void*&>((uintptr_t&)
machineContext.mc_gpregs.gp_x[4]);
++ return reinterpret_cast<void*&>((uintptr_t&) machineContext.sc_x[4]);
+#elif CPU(MIPS)
+ return reinterpret_cast<void*&>((uintptr_t&) machineContext.mc_regs[12]);
+#elif CPU(SPARC64)
