tools: elf: fix copy-elf when gcc links program

GCC will set the text size to `0` in a certain case that `rust-lld` did
not. This causes the elf copier to add about 512 MB to the image which
it otherwise shouldn't be doing.

Add a workaround that appears to fix the issue.

Signed-off-by: Sean Cross <sean@xobs.io>

tools/src/elf.rs

@@ -209,7 +209,7 @@ pub fn process_program(b: &[u8]) -> Result<ProgramDescription, ElfReadError> {
                 s.address()
             );
             continue;
-        } else if text_offset == 0 && s.size() != 0 {
+        } else if text_offset == 0 && (s.address() != 0 || s.size() != 0) {
             text_offset = s.address() as u32;
             text_size += s.size() as u32;
         } else {