improve ./gdb-lasercake
improve ./gdb-lasercake

Now it will prefer ggdb (for example for systems like OS X where
the built-in GDB is a very out of date version that can't deal
with gcc-4.7's debugging output, but macports' ggdb [in macports
package gdb] works fine).

Using `command -v` per http://stackoverflow.com/a/677212 ,
`man command`, and experimentation (they all agree).

Lasercake/Lasercake,Lasercake/Lasercake,idupree/Lasercake,elidupree/Lasercake,idupree/Lasercake,idupree/Lasercake,Lasercake/Lasercake,elidupree/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,elidupree/Lasercake,idupree/Lasercake,elidupree/Lasercake,idupree/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,elidupree/Lasercake,idupree/Lasercake,idupree/Lasercake