2lib: Add test_mockable attribute

Some tests mock library functions.  This previously worked due to adding

  CFLAGS += -Xlinker --allow-multiple-definition

to the test binaries.  But the new version of binutils seems to need
the default implementation to be weak if compiled with -O2 in some
cases.  Add test_mockable for use with functions where this is now
needed.

BUG=chromium:723906
BRANCH=none
TEST=Add CFLAGS += -O2 to the makefile, then make -j runtests
     Tests break before this change with -O2, and work afterwards

Change-Id: I95996a3e1086251442055765295a75de4c20ee3c
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/527601
Commit-Ready: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Rahul Chaudhry <rahulchaudhry@chromium.org>

firmware/2lib/include/2common.h

@@ -46,6 +46,18 @@ struct vb2_public_key;
 #  define VB2_DEBUG_RAW(format, args...)
 #endif
 
+/*
+ * Define test_mockable and for mocking functions when compiled for Chrome OS
+ * environment (that is, not for firmware).
+ */
+#ifndef test_mockable
+#ifdef CHROMEOS_ENVIRONMENT
+#define test_mockable __attribute__((weak))
+#else
+#define test_mockable
+#endif
+#endif
+
 /*
  * Alignment for work buffer pointers/allocations should be useful for any
  * data type. When declaring workbuf buffers on the stack, the caller should

firmware/include/vboot_api.h

@@ -39,7 +39,9 @@ typedef uint32_t VbError_t;
 /*
  * Define test_mockable for mocking functions.
  */
+#ifndef test_mockable
 #define test_mockable __attribute__((weak))
+#endif
 
 /*
  * Predefined error numbers.  Success is 0.  Errors are non-zero, but differ

firmware/lib20/packed_key.c

@@ -23,6 +23,7 @@ int vb2_verify_packed_key_inside(const void *parent,
 					key->key_offset, key->key_size);
 }
 
+test_mockable
 int vb2_unpack_key_buffer(struct vb2_public_key *key,
 			  const uint8_t *buf,
 			  uint32_t size)