let's call the variable SUNDIALS_CPPFLAGS

because it is for C preprocessor
let's call it GRACE_CPPFLAGS

because it is for C preprocessor
let's call it GRAPHVIZ_CPPFLAGS

because it is for C preprocessor
fix to match AC_LANG_PUSH & AC_LANG_POP
let's call it TCC_CPPFLAGS
let's call the variable SOSLIB_CPPFLAGS
-Wunused-but-set-variable
no need to overwrite nor substitute LIBS