binman: Drop .note section from ELF

Recent versions of binutils add a '.note.gnu.property' into the ELF file.
This is not required and interferes with the expected output. Drop it.

Also fix testMakeElf() to use a different file for input and output.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/elf.py b/tools/binman/elf.py
index af40024..c7ef74c 100644
--- a/tools/binman/elf.py
+++ b/tools/binman/elf.py
@@ -221,6 +221,9 @@
     .empty : {
         *(.empty)
     } :empty
+    /DISCARD/ : {
+        *(.note.gnu.property)
+    }
     .note : {
         *(.comment)
     } :note