Update configure

Since the patch "RISC-V: Add generic tune as default" has been commited into the trunk, the configure should also been updated. Here is the link:
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=20f593018519fec1602dc39c08ba2e674a2d8a1c

Signed-off-by: TelGome <93700071+TelGome@users.noreply.github.com>

Author: TelGome

configure

@@ -1400,7 +1400,7 @@ Optional Packages:
   --without-PACKAGE       do not use PACKAGE (same as --with-PACKAGE=no)
   --with-arch=rv64gc      Sets the base RISC-V ISA, defaults to rv64gc
   --with-abi=lp64d        Sets the base RISC-V ABI, defaults to lp64d
-  --with-tune=rocket      Set the base RISC-V CPU, defaults to rocket
+  --with-tune=generic     Set the base RISC-V CPU, defaults to GCC's default
   --with-isa-spec=20191213
                           Set the default ISA spec version, default to
                           20191213, available options: 2.2, 20190608, 20191213
@@ -4014,12 +4014,17 @@ fi
 if test ${with_tune+y}
 then :
   withval=$with_tune;
-else $as_nop
-  with_tune=rocket
 
 fi
 
 
+if test "x$with_tune" != "x"; then
+  WITH_TUNE="--with-tune=$with_tune"
+else
+  WITH_TUNE=""
+
+fi
+
 
 # Check whether --with-isa-spec was given.
 if test ${with_isa_spec+y}
@@ -4078,7 +4083,6 @@ WITH_ARCH=--with-arch=$with_arch
 
 WITH_ABI=--with-abi=$with_abi
 
-WITH_TUNE=--with-tune=$with_tune
 
 WITH_ISA_SPEC=--with-isa-spec=$with_isa_spec
 

configure.ac

@@ -94,12 +94,18 @@ AC_ARG_WITH(abi,
 	)
 
 AC_ARG_WITH(tune,
-	[AS_HELP_STRING([--with-tune=rocket],
-		[Set the base RISC-V CPU, defaults to rocket])],
-	[],
-	[with_tune=rocket]
+	[AS_HELP_STRING([--with-tune=generic],
+		[Set the base RISC-V CPU, defaults to GCC's default])],
+	[]
 	)
 
+if test "x$with_tune" != "x"; then
+  WITH_TUNE="--with-tune=$with_tune"
+else
+  WITH_TUNE=""
+
+fi
+
 AC_ARG_WITH(isa-spec,
 	[AS_HELP_STRING([--with-isa-spec=20191213],
 		[Set the default ISA spec version, default to 20191213, available options: 2.2, 20190608, 20191213])],
@@ -134,7 +140,7 @@ AS_IF([test "x$with_abi" = xdefault],
 
 AC_SUBST(WITH_ARCH, --with-arch=$with_arch)
 AC_SUBST(WITH_ABI, --with-abi=$with_abi)
-AC_SUBST(WITH_TUNE, --with-tune=$with_tune)
+AC_SUBST(WITH_TUNE)
 AC_SUBST(WITH_ISA_SPEC, --with-isa-spec=$with_isa_spec)
 AC_SUBST(WITH_SIM, $with_sim)
 AC_SUBST(WITH_LANGUAGES, $with_languages)