cmd/link: use correct alignment in PE DWARF sections

Set the correct section flags to insure that .debug_* sections are
using 1-byte alignment instead of the default. This seems to be
important for later versions of LLVM-mingw on windows (shows up on the
windows/arm64 builder).

Updates #46406.

Change-Id: I023d5208374f867552ba68b45011f7990159868f
Reviewed-on: https://go-review.googlesource.com/c/go/+/324763
Trust: Than McIntosh <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Run-TryBot: Than McIntosh <[email protected]>
TryBot-Result: Go Bot <[email protected]>

Author: thanm

src/cmd/link/internal/ld/pe.go

@@ -475,7 +475,7 @@ func (f *peFile) addDWARFSection(name string, size int) *peSection {
 	off := f.stringTable.add(name)
 	h := f.addSection(name, size, size)
 	h.shortName = fmt.Sprintf("/%d", off)
-	h.characteristics = IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_DISCARDABLE | IMAGE_SCN_CNT_INITIALIZED_DATA
+	h.characteristics = IMAGE_SCN_ALIGN_1BYTES | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_DISCARDABLE | IMAGE_SCN_CNT_INITIALIZED_DATA
 	return h
 }