Revert "Alwayze zero BSS in bbl.py"

New platforms should use ELF loaders that actually adhere to the
standard, not keep requiring this bodge. If they really find it so hard
to do that then they can have their own special builds, but this hack
should stay out of the normal QEMU build.

This reverts commit a00ccaf.

pycheribuild/projects/cross/bbl.py

@@ -62,7 +62,7 @@ class BuildBBLBase(CrossCompileAutotoolsProject):
  kernel_class = None
  cross_install_dir = DefaultInstallDir.ROOTFS_OPTBASE
  without_payload = False
- enable_zero_bss = True
+ enable_zero_bss = False
  custom_payload: Optional[str] = None
  mem_start = "0x80000000"
  supported_architectures = (
@@ -206,6 +206,7 @@ class BuildBBLNoPayloadGFE(BuildBBLNoPayload):
  target = "bbl-gfe"
  default_directory_basename = "bbl" # reuse same source dir
  build_dir_suffix = "-gfe" # but not the build dir
+ enable_zero_bss = True
 
  _default_install_dir_fn = ComputedDefaultValue(
  function=_bbl_install_dir,