Use native TLS on all architectures except aarch64

Update mingw-w64 to the latest version, where native TLS works
with LLVM/LLD.

Dockerfile

@@ -46,7 +46,7 @@ RUN cd llvm && mkdir build && cd build && cmake \
 
 RUN git clone git://git.code.sf.net/p/mingw-w64/mingw-w64 && \
     cd mingw-w64 && \
-    git checkout 124a62c7cc32909b7c6c57e901579de48e3a35d8
+    git checkout f25c9a89ed2b2d98bc2658cfa4dc97a2c837c725
 
 
 ENV TOOLCHAIN_PREFIX=/build/prefix

wrappers/clang-target-wrapper

@@ -9,16 +9,21 @@ i686)
 	# Dwarf is the default for i686, but currently there's an issue
 	# in libunwind with unwinding clang generated dwarf opcodes on 32 bit
 	# x86, pending resolution at https://reviews.llvm.org/D38680.
-	EH_FLAG=-fsjlj-exceptions
-	;;
-armv7|aarch64)
-	# Dwarf is the default for these targets.
-	EH_FLAG=
+	ARCH_FLAGS=-fsjlj-exceptions
 	;;
 x86_64)
 	# Explicitly request dwarf on x86_64; SEH is the default there but
 	# libcxxabi lacks support for it.
-	EH_FLAG=-fdwarf-exceptions
+	ARCH_FLAGS=-fdwarf-exceptions
+	;;
+armv7)
+	# Dwarf is the default here.
+	ARCH_FLAGS=
+	;;
+aarch64)
+	# Dwarf is the default on aarch64; enable emulated TLS since native
+	# TLS isn't implemented yet.
+	ARCH_FLAGS=-femulated-tls
 	;;
 esac
-$DIR/$EXE -target $TARGET -rtlib=compiler-rt -stdlib=libc++ -fuse-ld=lld $EH_FLAG -Qunused-arguments -femulated-tls "$@"
+$DIR/$EXE -target $TARGET -rtlib=compiler-rt -stdlib=libc++ -fuse-ld=lld $ARCH_FLAGS -Qunused-arguments "$@"