bsp: add zynq7000

Device fix

Pulls

tools/building.py: more descriptive on error

Print the command that failed to execute and try to tell the reason to
fall.

Ls1b

We don't need the crt0 from the toolchain.

Scons: fix the Win32Spawn

Windows(tm) CreateProcess does not use the env passed to it to find the
executables. So we have to modify our own PATH to make Popen work. Also,
detect the cmd build-in commands and execute it directly.

Tested on MDK toolchain on RB4088 and the MSVS toolchain on simulator
BSP.

Update SConscript

Update stm32_rom.ld

Update rtconfig.py

add keil fpu support and gcc fpu support in scons building

Pulls