Merging r356982:

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r356982 | mstorsjo | 2019-03-26 02:02:44 -0700 (Tue, 26 Mar 2019) | 12 lines

[llvm-dlltool] Set a proper machine type for weak symbol object files

This makes GNU binutils not reject the libraries outright.

GNU ld handles weak externals slightly differently though, so it
can't use them for aliases in import libraries, but this makes GNU
ld able to use the rest of the import libraries.

LLD accepted object files with machine type 0 aka
IMAGE_FILE_MACHINE_UNKNOWN.

Differential Revision: https://reviews.llvm.org/D59742
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llvm-svn: 360750

Author: tstellar

llvm/lib/Object/COFFImportFile.cpp

@@ -496,7 +496,7 @@ NewArchiveMember ObjectFactory::createWeakExternal(StringRef Sym,
 
   // COFF Header
   coff_file_header Header{
-      u16(0),
+      u16(Machine),
       u16(NumberOfSections),
       u32(0),
       u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section))),

llvm/test/tools/llvm-dlltool/coff-weak-exports.def

@@ -1,5 +1,6 @@
 ; RUN: llvm-dlltool -m i386:x86-64 --input-def %s --output-lib %t.a
 ; RUN: llvm-nm %t.a | FileCheck %s
+; RUN: llvm-readobj %t.a | FileCheck -check-prefix=ARCH %s
 
 LIBRARY test.dll
 EXPORTS
@@ -26,3 +27,5 @@ ImpLibName3 = kernel32.Sleep
 ; CHECK-NEXT: W __imp_ImpLibName2
 ; CHECK:      T ImpLibName3
 ; CHECK-NEXT: T __imp_ImpLibName3
+
+; ARCH-NOT: unknown arch