[lld-macho] Fix category merging sed issue - Try nr.2 (#112981)

We replace sed with awk as I couldn't find a syntax that works
consistently on Linux/Mac for sed.
Repro'ed original issue on Mac and confirmed working now on Mac/Linux.

lld/test/MachO/objc-category-merging-minimal.s

@@ -30,7 +30,7 @@
 
 ############ Test merging skipped due to invalid category name ############
 # Modify __OBJC_$_CATEGORY_MyBaseClass_$_Category01's name to point to L_OBJC_IMAGE_INFO+3
-# RUN: sed -E '/^__OBJC_\$_CATEGORY_MyBaseClass_\$_Category01:/ { n; s/^[ \t]*\.quad[ \t]+l_OBJC_CLASS_NAME_$/\t.quad\tL_OBJC_IMAGE_INFO+3/}' merge_cat_minimal.s > merge_cat_minimal_bad_name.s
+# RUN: awk '/^__OBJC_\$_CATEGORY_MyBaseClass_\$_Category01:/ { print; getline; sub(/^[ \t]*\.quad[ \t]+l_OBJC_CLASS_NAME_$/, "\t.quad\tL_OBJC_IMAGE_INFO+3"); print; next } { print }' merge_cat_minimal.s > merge_cat_minimal_bad_name.s
 
 # Assemble the modified source
 # RUN: llvm-mc -filetype=obj -triple=arm64-apple-macos -o merge_cat_minimal_bad_name.o merge_cat_minimal_bad_name.s