Fix compatibility with Linaro toolchains for building ARM binaries

Add DISCARD directives to the linker scripts and also -marm option
to GCC command line. Without this, certain toolchains may build
Thumb2 code by default. Also junk sections may be present in the
final binary and they need to be removed.

This helps at least when using the following Linaro toolchain:
gcc-linaro-5.1-2015.08-x86_64_arm-linux-gnueabihf.tar.xz
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Reviewed-by: Bernhard Nortmann <bernhard.nortmann@web.de>

Makefile

@@ -121,7 +121,7 @@ sunxi-%: %.c
 
 fel-pio.bin: fel-pio.elf fel-pio.nm
 
-ARM_ELF_FLAGS = -Os -fpic -Wall
+ARM_ELF_FLAGS = -Os -marm -fpic -Wall
 ARM_ELF_FLAGS += -fno-common -fno-builtin -ffreestanding -nostdinc
 ARM_ELF_FLAGS += -mno-thumb-interwork -fno-stack-protector -fno-toplevel-reorder
 ARM_ELF_FLAGS += -Wstrict-prototypes -Wno-format-nonliteral -Wno-format-security

boot_head.lds

@@ -14,10 +14,15 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-     SECTIONS
-     {
-       . = 0x40007000;
-       .text : { *(.text) }
-     }
-
 
+SECTIONS
+{
+	. = 0x40007000;
+	.text : { *(.text) }
+	/DISCARD/ : { *(.dynstr*) }
+	/DISCARD/ : { *(.dynamic*) }
+	/DISCARD/ : { *(.plt*) }
+	/DISCARD/ : { *(.interp*) }
+	/DISCARD/ : { *(.gnu*) }
+	/DISCARD/ : { *(.note*) }
+}

fel-pio.lds

@@ -14,10 +14,15 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-     SECTIONS
-     {
-       . = 0x2000;
-       .text : { *(.text) }
-     }
-
 
+SECTIONS
+{
+	. = 0x2000;
+	.text : { *(.text) }
+	/DISCARD/ : { *(.dynstr*) }
+	/DISCARD/ : { *(.dynamic*) }
+	/DISCARD/ : { *(.plt*) }
+	/DISCARD/ : { *(.interp*) }
+	/DISCARD/ : { *(.gnu*) }
+	/DISCARD/ : { *(.note*) }
+}

fel-sdboot.lds

@@ -14,10 +14,15 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-     SECTIONS
-     {
-       . = 0x0030;
-       .text : { *(.text) }
-     }
-
 
+SECTIONS
+{
+	. = 0x0030;
+	.text : { *(.text) }
+	/DISCARD/ : { *(.dynstr*) }
+	/DISCARD/ : { *(.dynamic*) }
+	/DISCARD/ : { *(.plt*) }
+	/DISCARD/ : { *(.interp*) }
+	/DISCARD/ : { *(.gnu*) }
+	/DISCARD/ : { *(.note*) }
+}

jtag-loop.lds

@@ -14,10 +14,15 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-     SECTIONS
-     {
-       . = 0x0030;
-       .text : { *(.text) }
-     }
-
 
+SECTIONS
+{
+	. = 0x0030;
+	.text : { *(.text) }
+	/DISCARD/ : { *(.dynstr*) }
+	/DISCARD/ : { *(.dynamic*) }
+	/DISCARD/ : { *(.plt*) }
+	/DISCARD/ : { *(.interp*) }
+	/DISCARD/ : { *(.gnu*) }
+	/DISCARD/ : { *(.note*) }
+}