Incompatible with -gsplit-dwarf=single and -gsplit-dwarf=split (clang)

[jankratochvil]

-gsplit-dwarf itself works fine. But -gsplit-dwarf=single (and even -gsplit-dwarf=split which is the same as -gsplit-dwarf) will produce unloadable debug info.

icecream-1.3-4.fc34.x86_64

Actual:

Reading symbols from ./main...
warning: Could not find DWO CU icecc-201616_c274b459.o(0xadb46cb729222933) referenced by CU at offset 0xd8 [in module /quad/home/jkratoch/t/splitsingle/main]
warning: Could not find DWO CU icecc-201617_cfd7b459.o(0x52d23d48271d0185) referenced by CU at offset 0x144 [in module /quad/home/jkratoch/t/splitsingle/main]

$ llvm-dwarfdump 110.o
.debug_info contents:
...
0x0000000b: DW_TAG_compile_unit
...
              DW_AT_GNU_dwo_name        ("icecc-201615_c4e1b459.o")
...
.debug_info.dwo contents:
...
0x0000000b: DW_TAG_compile_unit
              DW_AT_name        ("110.C")
              DW_AT_GNU_dwo_name        ("icecc-201615_c4e1b459.o")
...
0x00000019:   DW_TAG_variable
                DW_AT_name      ("i110")

Expected:

Reading symbols from ./main...

$ llvm-dwarfdump 110.o
.debug_info contents:
...
0x0000000b: DW_TAG_compile_unit
...
              DW_AT_GNU_dwo_name        ("110.o")
...
.debug_info.dwo contents:
...
0x0000000b: DW_TAG_compile_unit
              DW_AT_name        ("110.C")
              DW_AT_GNU_dwo_name        ("110.o")
...
0x00000019:   DW_TAG_variable
                DW_AT_name      ("i110")

run.txt