In build
MyVar is here
Makeflags is 
Makeoverrides is 
make clean MYVAR=gone
make[1]: Entering directory `/sgi/ids1c/swdev/cme/clouseau/misc/tyt'
In clean
MyVar is gone
Makeflags is w -- MYVAR=gone
Makeoverrides is MYVAR=gone
make final
make[2]: Entering directory `/sgi/ids1c/swdev/cme/clouseau/misc/tyt'
In final
MyVar is gone
Makeflags is w -- MYVAR=gone
Makeoverrides is MYVAR=gone
make[2]: Leaving directory `/sgi/ids1c/swdev/cme/clouseau/misc/tyt'
make[1]: Leaving directory `/sgi/ids1c/swdev/cme/clouseau/misc/tyt'