Fix an error on Solaris 10 like:
./mkdep: /opt/solarisstudio12.3/bin/cc -D_STDC_C99=: not found
When configure get some compiler option like:
checking for /opt/solarisstudio12.3/bin/cc option to accept ISO C99...
-D_STDC_C99=
Makefile will contain:
CC = /opt/solarisstudio12.3/bin/cc -D_STDC_C99=
And if we use '-c "$(CC)"' mkdep will set and try to run:
CC="/opt/solarisstudio12.3/bin/cc -D_STDC_C99=", which is incorrect.
Remove the quotes to allow mkdep to set CC with the compiler name and
set flags with the option.