[OOB 5.6 r2] DISCO_F429ZI does not run by Makefile exported binary

### Description
- Type: Bug
- Priority: Major

---------------------------------------------------------------
## Bug

**Target**
DISCO_F429ZI

**Toolchain:**
GCC_ARM

**Toolchain version:**
arm-none-eabi-gcc.exe (GNU Tools for ARM Embedded Processors 6-2017-q1-update) 6.3.1 20170215 (release) [ARM/embedded-6-branch revision 245512]
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

**mbed-cli version:**
1.2.0

**mbed-os sha:**
mbed-os-example-uvisor (a09159266307)
`- mbed-os (6e087488e101)

**DAPLink version:**
0221

**Expected behavior**
The example run on the target without error.

**Actual behavior**
There is no log output at runtime. It looks not startup correctly.

**Steps to reproduce**

$ mbed import mbed-os-example-uvisor
$ cd mbed-os-example-uvisor
$ mbed update mbed-os-5.6-oob2
$ mbed export -m DISCO_F429ZI -i make_gcc_arm
$ make

Flash the binary from BUILD/mbed-os-example-uvisor.bin to the target drive.

Note that the binary created by ```mbed compile -m DISCO_F429ZI -t GCC_ARM -f``` works fine. And also, binary file size is slightly different between GCC_ARM build and make_gcc_arm build (see below).

|Toolchain|binary file size|
|----------|-------------:|
|GCC_ARM|63KB|
|make_gcc_arm|112KB|

**Misc. info**

[Build log file](https://github.com/ARMmbed/mbed-os-example-uvisor/files/1317364/example-uvisor-build.txt)
[Makefile](https://github.com/ARMmbed/mbed-os-example-uvisor/files/1317369/Makefile.txt)

The [mbed-os-example-uvisor-thread](https://github.com/ARMmbed/mbed-os-example-uvisor-thread) has also same problem (I did not raise a new issue, since the root cause may be same).

Start with the attached Makefile and build log, reproducing the DISCO_F429ZI build with mbed export and make. Compare the make_gcc_arm output with the working mbed compile binary and verify the exported binary produces runtime log output on the target. Done means the Makefile-generated binary runs like the GCC_ARM build.

Written by the indexing model from the issue text.