ldso: Force disable -mlong-calls when compiling ldso for ARC

ldso: Force disable -mlong-calls when compiling ldso for ARC

Even though by default for ARC uClibc gets compiled with
disabled long-calls user may provide UCLIBC_EXTRA_CFLAGS
with "-mlong-calls". With this option uClibc will be
successfully compiled but later it will fail in runtime
because dynamic loader cannot deal with relocations
at least very early on its start.

In particular it will be seen as call to non-relocated
symbol _dl_parse_dynamic_info() which ends-up as a segfault
like this:
------------------------>8--------------------
potentially unexpected fatal signal 11.
Path: /bin/test
CPU: 0 PID: 63 Comm: test Not tainted 4.5.2 #7
task: 9f13f180 ti: 9f166000 task.ti: 9f166000

[ECR   ]: 0x00040000 => Insn could not be fetched
[EFA   ]: 0x0000283c
[BLINK ]: 0x2000407c
[ERET  ]: 0x283c
    @No matching VMA found
[STAT32]: 0x8008009e : IE U
BTA: 0x0000283c  SP: 0x5fef5ccc  FP: 0x00000000
LPS: 0x20004080 LPE: 0x20004064 LPC: 0x00000000
r00: 0x20006684 r01: 0x5fef5db0 r02: 0x00000000
r03: 0x20000000 r04: 0x80808080 r05: 0x2f2f2f2f
r06: 0x41464d00 r07: 0x00000080 r08: 0x000000dd
r09: 0x00000000 r10: 0x00000073 r11: 0x80808080
r12: 0x2000407c r13: 0x20000000 r14: 0x5fef5e74
r15: 0x000ceb3c r16: 0x5fef5e7c r17: 0x5fef5d44
r18: 0x000ceb0c r19: 0xffffffff r20: 0x000ceb1c
r21: 0x00000000 r22: 0x00000000 r23: 0x000d08a5
r24: 0x00000000 r25: 0x80808080

Segmentation fault
------------------------>8--------------------

Solution to this issue is simple we make sure dynamic
loader never gets compiled with "-mlong-calls" by forcing
"-mno-long-calls" on it.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Anton Kolesov <akolesov@synopsys.com>
Cc: linux-snps-arc@lists.infradead.org