Fix riscv build, no longer works with python2

Building riscv no longer works with python2:

> python ./config/riscv/arch-canonicalize -misa-spec=20191213 rv64gc
  File "./config/riscv/arch-canonicalize", line 229
    print(f"ERROR: Unhandled conditional dependency: '{ext_name}' with condition:", file=sys.stderr)
                                                                                 ^
SyntaxError: invalid syntax

On systems that have python aliased to python2 we chose that, even
when python3 is available.  Don't.

	* config.gcc (riscv*-*-*): Look for python3, then fall back
	to python.  Never use python2.

diff --git a/gcc/config.gcc b/gcc/config.gcc
index 55e171816dcafe0974279dc211dc9ef156852fe0..56246387ef55c346c2eb00d11aa5147faaa521b5 100644 (file)
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -4782,7 +4782,7 @@ case "${target}" in
                        exit 1
                        ;;
                esac
-               PYTHON=`which python || which python3 || which python2`
+               PYTHON=`which python3 || which python`
                if test "x${PYTHON}" != x; then
                        with_arch=`${PYTHON} ${srcdir}/config/riscv/arch-canonicalize -misa-spec=${with_isa_spec} ${with_arch}`
                fi