[llvm-objcopy] - Fix --compress-debug-sections when there are relocations.

When --compress-debug-sections is given,
llvm-objcopy removes the uncompressed sections and adds compressed to the section list.
This makes all the pointers to old sections to be outdated.

Currently, code already has logic for replacing the target sections of the relocation
sections. But we also have to update the relocations by themselves.

This fixes https://bugs.llvm.org/show_bug.cgi?id=40885.

Differential revision: https://reviews.llvm.org/D58960

llvm-svn: 355821
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 0a360d0..70eb2e8 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
@@ -57,7 +57,8 @@
 
 # CHECK-FLAGS: Relocations [
 # CHECK-FLAGS-NEXT:   .rela.debug_foo {
-# CHECK-FLAGS-NEXT:     0x1 R_X86_64_32 - 0x0
+# CHECK-FLAGS-NEXT:     0x1 R_X86_64_32 .zdebug_foo 0x0
+# CHECK-FLAGS-NEXT:     0x2 R_X86_64_32 .notdebug_foo 0x0
 # CHECK-FLAGS-NEXT:   }
 # CHECK-FLAGS-NEXT: ]