chained-fixups.yaml: force little-endian output

`__LINK_EDIT` contents are little-endian, so the whole file must be.
Might fix the test on big-endian systems.

Author: nico

llvm/test/tools/llvm-objdump/MachO/chained-fixups.yaml

@@ -25,6 +25,7 @@
 ##   clang -target=x86_64-apple-macos12 -dynamiclib -isysroot Inputs/MacOSX.sdk dylib.s -o libdylib.dylib
 ##   obj2yaml --raw-segment=data libdylib.dylib
 --- !mach-o
+IsLittleEndian:  true
 FileHeader:
   magic:           0xFEEDFACF
   cputype:         0x1000007