Configure: add -Wmisleading-indentation to strict warnings flags.

The warning flag in question was added in GCC version 6, hence
addition has to be conditional.

Reviewed-by: Ben Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/4401)

diff --git a/Configure b/Configure
index 326a3ff434c07e7538dbb4adb0029c05e388eab4..b1b847c59d6a0bea5e09832e9590398eb447dd2c 100755 (executable)
--- a/Configure
+++ b/Configure
@@ -148,6 +148,7 @@ my $clang_devteam_warn = ""
         . " -Wconditional-uninitialized"
         . " -Wincompatible-pointer-types-discards-qualifiers"
         . " -Wmissing-variable-declarations"
+        . " -Wno-unknown-warning-option"
         ;
 
 # This adds backtrace information to the memory leak info.  Is only used
@@ -1327,8 +1328,11 @@ if (defined($predefined{__clang__}) && !$disabled{asm}) {
 if ($strict_warnings)
        {
        my $wopt;
-       die "ERROR --strict-warnings requires gcc or gcc-alike"
-            unless defined($predefined{__GNUC__});
+       my $gccver = $predefined{__GNUC__} // -1;
+
+       die "ERROR --strict-warnings requires gcc[>=4] or gcc-alike"
+            unless $gccver >= 4;
+       $gcc_devteam_warn .= " -Wmisleading-indentation" if $gccver >= 6;
        foreach $wopt (split /\s+/, $gcc_devteam_warn)
                {
                $config{cflags} .= " $wopt" unless ($config{cflags} =~ /(?:^|\s)$wopt(?:\s|$)/)