[dsymutil] Implement support for universal mach-o object files.

This patch allows llvm-dsymutil to read universal (aka fat) macho object
files and archives. The patch touches nearly everything in the BinaryHolder,
but it is fairly mechinical: the methods that returned MemoryBufferRefs or
ObjectFiles now return a vector of those, and the high-level access function
takes a triple argument to select the architecture.

There is no support yet for handling fat executables and thus no support for
writing fat object files.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243096 91177308-0d34-0410-b5e6-96231b3b80d8

test/tools/dsymutil/ARM/fat-arch-not-found.test

@@ -0,0 +1,13 @@
+# REQUIRES: object-emission
+# RUN: llvm-dsymutil -oso-prepend-path=%p/../Inputs -y %s -o - 2>&1 | FileCheck %s
+
+---
+triple:          'armv7-apple-darwin'
+objects:
+  - filename: libfat-test.a(fat-test.o)
+    symbols:
+      - { sym: _armv7_var, objAddr: 0x0, binAddr: 0x1000, size: 0x4 }
+...
+
+# CHECK: libfat-test.a(fat-test.o): No object file for requested architecture
+

test/tools/dsymutil/ARM/lit.local.cfg

@@ -0,0 +1,2 @@
+if not 'X86' in config.root.targets:
+    config.unsupported = True

test/tools/dsymutil/Inputs/fat-test.c

@@ -0,0 +1,17 @@
+/* Compile with:
+   clang -c -g -arch x86_64h -arch x86_64 -arch i386 fat-test.c
+   libtool -static -o libfat-test.a fat-test.o
+
+   To reduce the size of the fat .o:
+   lipo -thin i386 -o fat-test.i386.o fat-test.o 
+   lipo -thin x86_64 -o fat-test.x86_64.o fat-test.o 
+   lipo -thin x86_64h -o fat-test.x86_64h.o fat-test.o 
+   lipo -create -arch x86_64h fat-test.x86_64h.o -arch x86_64 fat-test.x86_64.o -arch i386 fat-test.i386.o -o fat-test.o -segalign i386 8 -segalign x86_64 8 -segalign x86_64h 8
+ */
+#ifdef __x86_64h__
+int x86_64h_var;
+#elif defined(__x86_64__)
+int x86_64_var;
+#else
+int i386_var;
+#endif

test/tools/dsymutil/X86/fat-archive-input-i386.test

@@ -0,0 +1,16 @@
+# REQUIRES: object-emission
+# RUN: llvm-dsymutil -oso-prepend-path=%p/../Inputs -y %s -o - | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+
+---
+triple:          'i386-apple-darwin'
+objects:
+  - filename: libfat-test.a(fat-test.o)
+    symbols:
+      - { sym: _i386_var, objAddr: 0x0, binAddr: 0x1000, size: 0x4 }
+...
+
+# CHECK: .debug_info contents:
+# CHECK: DW_TAG_variable
+# CHECK-NOT: {{DW_TAG|NULL}}
+# CHECK:  DW_AT_name{{.*}}"i386_var"
+

test/tools/dsymutil/X86/fat-object-input-x86_64.test

@@ -0,0 +1,16 @@
+# REQUIRES: object-emission
+# RUN: llvm-dsymutil -oso-prepend-path=%p/../Inputs -y %s -o - | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+
+---
+triple:          'x86_64-apple-darwin'
+objects:
+  - filename: fat-test.o
+    symbols:
+      - { sym: _x86_64_var, objAddr: 0x0, binAddr: 0x1000, size: 0x4 }
+...
+
+# CHECK: .debug_info contents:
+# CHECK: DW_TAG_variable
+# CHECK-NOT: {{DW_TAG|NULL}}
+# CHECK:  DW_AT_name{{.*}}"x86_64_var"
+

test/tools/dsymutil/X86/fat-object-input-x86_64h.test

@@ -0,0 +1,16 @@
+# REQUIRES: object-emission
+# RUN: llvm-dsymutil -oso-prepend-path=%p/../Inputs -y %s -o - | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+
+---
+triple:          'x86_64h-apple-darwin'
+objects:
+  - filename: fat-test.o
+    symbols:
+      - { sym: _x86_64h_var, objAddr: 0x0, binAddr: 0x1000, size: 0x4 }
+...
+
+# CHECK: .debug_info contents:
+# CHECK: DW_TAG_variable
+# CHECK-NOT: {{DW_TAG|NULL}}
+# CHECK:  DW_AT_name{{.*}}"x86_64h_var"
+