fix ElfObj::common_block size

- fix Issue 11237

- Need to explicitly pass the size of the defined common
  symbol as it can't be computed from the symbol type.
struct initializer are not weak symbols

- fix Issue 11237

- The function outdata will take care of the
  BSS optimization for DTallzeros.
add test case for Issue 11237

- fix OS name of linux in Makefile
Merge pull request #2701 from dawgfoto/fix11237

fix Issue 11237