Extracts the full compiler path and feeds it to cmake.

Previously, specifying the compiler name with a variable
to configure ("configure CC=gcc") lead to CMake complaining
that <builddir>/$CC was not a valid path. This patch fixes
this by extracting the full path with "which <compiler>".
Should fix issue #355.

cmake/Scripts/configure

@@ -453,11 +453,11 @@ for a in "${VARS[@]}"; do
       ;;
     CC=*)
       # special processing for compiler options
-      a=${a#CC=}
+      a=`which ${a#CC=}`
       c_compiler=" -DCMAKE_C_COMPILER=\"${a/\"/\\\"}\""
       ;;
     CXX=*)
-      a=${a#CXX=}
+      a=`which ${a#CXX=}`
       cxx_compiler=" -DCMAKE_CXX_COMPILER=\"${a/\"/\\\"}\""
       ;;
     CFLAGS=*)
@@ -469,7 +469,7 @@ for a in "${VARS[@]}"; do
       cxx_opts=" -DCMAKE_CXX_FLAGS=\"${a/\"/\\\"}\""
       ;;
     FC=*)
-      a=${a#FC=}
+      a=`which ${a#FC=}`
       fort_compiler=" -DCMAKE_Fortran_COMPILER=\"${a/\"/\\\"}\""
       ;;
     FFLAGS=*)