Update SDK:s/cmake-startup for next release with cmake included

[josefwegner]

For the next SDK-Addon release that includes cmake, please update SDK:s/cmake-startup.

Issue:
abc-shell uses a hardcoded PATH if no PATH environment variable is set. If there is a PATH environment variable, abc-shell will use it without modification. Since most users do not set a custom PATH, cmake-startup will override abc-shell's path and render it useless. This needs to be addressed before the release.

Example:

3. > RAM Disk: > setenv PATH /cmake-amiga/bin
3. > RAM Disk: > sh
/RAM Disk> echo $PATH
/cmake-amiga/bin

Solution:
One solution would be to set the complete default PATH if there is no PATH env in cmake-startup:

assign cmake-amiga: SDK:cmake

GetEnv >NIL: *>NIL: PATH
If WARN
  setenv PATH /cmake-amiga/bin:/gcc/bin:/SDK/C:/SDK/Local/C:/SDK/Local/newlib/bin:/SDK/Local/clib2/bin:/C:.
Else
  setenv PATH /cmake-amiga/bin:${PATH}
EndIf

path ADD cmake-amiga:bin