apply neon-vfpv4 mfpu flag for cortex-a15 cpu

Change-Id: I663d8b0c169113727dd2c5c12c0c896d2d8efe20
arm:thumb:compiling with  O2

The compiler was targeting -Os before this commit, now it targets -O2

Change-Id: I07929b161610acd0a2cebb63a383720b6078d59c
clang:compiling with O3 flag

Change-Id: Id4d56ee3b6b250674df852ff8b1c583c3c80f0fc
No error on array-bounds

O3 flag raises an error when array subscript is above array bounds, passing Wno-array-bounds prevents the compiler to stop working when facing this error

Change-Id: Ide8d80360bb2ee351b8aa5bebb4a2c1f58a26ea7
LD_FLAGS: use JustArchi V3's flags

Change-Id: I04e47f3f534f58244bb36929b8017a2da8481f84
Enabled gcc's automatic vectorization for the whole build

Change-Id: Idfcc7f1810605308d64667c06e2b1b823a6cee7c
compile the whole build with O3 flag

Change-Id: I92d5951a90be2ed8e69aa5f67d1f1ff60507c790
No errors on strict overflow

Wno-strict-overflow prevents the compilers to stop its compilation upon strict overflow

Change-Id: I5483325133002ab44034198c3f784f299e74cfd1
gitignore: ignore temp files(*.*~) produced by gedit

Change-Id: Ie4e59f611f8a73fbe3674f5e4c71384c5be98c46
Enabled Swing Modulo Scheduling

-fmodulo-sched and -fmodulo-sched-allow-regmoves are fairly new optimizations not currently automatically enabled at any -O level.
These options improve loop scheduling – more information can be found there: https://gcc.gnu.org/news/sms.html.

Change-Id: I69b3fa05e0d5d262ddbe5ec5da0ba0573b1db38a
clang: updated unsupported flags

fgcse-las, fgcse-sm and fgcse-after-reload are not supported by clang, we have to notice the compiler to ignore them

Change-Id: I136dfc309c6f9801285458d134de8fcdc757b4bf
clang:updated unknown cflags

-fmodulo-sched and -fmodulo-sched-allow-regmoves are not supported by clang, so we need to add them to the unknown flag list

Change-Id: I75b8b4b62732f1a8f006e25127b8edadaf976920