Makefile: pass -ansi option to cmd_gen_envp

Without the '-ansi' option, the 'linux' string in env. files is replaced
with the string '1 '. For example, in the
board/armadeus/opos6uldev/opos6uldev.env file,

kernelimg=opos6ul-linux.bin

becomes

kernelimg=opos6ul-1 .bin

in the include/generated/env.in file.

That's because 'linux' is a System-specific Predefined Macros. [1]

Pass the '-ansi' option as suggested by the GCC documentation. [1]
The option "disables recognition of C++ style ‘//’ comments" [2] so fix the
two .env files using C++ comment style for the SPDX licence.

[1] https://gcc.gnu.org/onlinedocs/gcc-13.2.0/cpp/System-specific-Predefined-Macros.html
[2] https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html#index-ANSI-support



Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>