[llvm-objcopy][NFC] Consistenly use two dashes for flags in tests.

Summary:
As pointed out in D53667, our use of hyphens in flags can be inconsistent, mixing `-` with `--`. This change makes all long style flags use `--`.

Automatically changed via:

```
find test/tools/llvm-objcopy/ELF -type f | xargs sed -i 's/ -\([a-zA-Z]\{3\}\)/ --\1/g'
```

Two false positives were manually fixed/reverted.

Reviewers: jhenderson, espindola, alexshap

Reviewed By: jhenderson

Subscribers: emaste, javed.absar, arichardson, fedor.sergeev, jakehehrlich, llvm-commits

Differential Revision: https://reviews.llvm.org/D56513

llvm-svn: 350944
diff --git a/llvm/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-gnu.test b/llvm/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-gnu.test
index 7199b2e..0a360d0 100644
--- a/llvm/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-gnu.test
+++ b/llvm/test/tools/llvm-objcopy/ELF/compress-debug-sections-zlib-gnu.test
@@ -4,12 +4,12 @@
 # RUN: llvm-objcopy --compress-debug-sections=zlib-gnu %t.o %t-compressed.o
 # RUN: llvm-objcopy --decompress-debug-sections %t-compressed.o %t-decompressed.o
 
-# RUN: llvm-objdump -s %t.o -section=.debug_foo | FileCheck %s
+# RUN: llvm-objdump -s %t.o --section=.debug_foo | FileCheck %s
 # RUN: llvm-objdump -s %t-compressed.o | FileCheck %s --check-prefix=CHECK-COMPRESSED
-# RUN: llvm-readobj -relocations -s %t-compressed.o | FileCheck %s --check-prefix=CHECK-FLAGS
-# RUN: llvm-readobj -relocations -s %t-decompressed.o | FileCheck %s --check-prefix=CHECK-HEADER
-# RUN: llvm-readobj -relocations -s %t.o | FileCheck %s --check-prefix=CHECK-HEADER
-# RUN: llvm-objdump -s %t-decompressed.o -section=.debug_foo | FileCheck %s
+# RUN: llvm-readobj --relocations -s %t-compressed.o | FileCheck %s --check-prefix=CHECK-FLAGS
+# RUN: llvm-readobj --relocations -s %t-decompressed.o | FileCheck %s --check-prefix=CHECK-HEADER
+# RUN: llvm-readobj --relocations -s %t.o | FileCheck %s --check-prefix=CHECK-HEADER
+# RUN: llvm-objdump -s %t-decompressed.o --section=.debug_foo | FileCheck %s
 
 # CHECK: .debug_foo:
 # CHECK-NEXT: 0000 00000000 00000000