haiku: non-x86 spins use a normal libstdc++ filename. Handle the differences.

Fixes Bugzilla #3730.

configure

@@ -24031,7 +24031,32 @@ $as_echo "#define SDL_FILESYSTEM_HAIKU 1" >>confdefs.h
         fi
         # The Haiku platform requires special setup.
         SOURCES="$srcdir/src/main/haiku/*.cc $SOURCES"
-        EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lroot -lbe -lmedia -lgame -ldevice -ltextencoding -lstdc++.r4"
+        EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lroot -lbe -lmedia -lgame -ldevice -ltextencoding"
+        # Haiku's x86 spins use libstdc++.r4.so (for binary compat?), but
+        #  other spins, like x86-64, use a more standard "libstdc++.so.*"
+        as_ac_File=`$as_echo "ac_cv_file_"/boot/system/lib/libstdc++.r4.so"" | $as_tr_sh`
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for \"/boot/system/lib/libstdc++.r4.so\"" >&5
+$as_echo_n "checking for \"/boot/system/lib/libstdc++.r4.so\"... " >&6; }
+if eval \${$as_ac_File+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  test "$cross_compiling" = yes &&
+  as_fn_error $? "cannot check for file existence when cross compiling" "$LINENO" 5
+if test -r ""/boot/system/lib/libstdc++.r4.so""; then
+  eval "$as_ac_File=yes"
+else
+  eval "$as_ac_File=no"
+fi
+fi
+eval ac_res=\$$as_ac_File
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+if eval test \"x\$"$as_ac_File"\" = x"yes"; then :
+  EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lstdc++.r4"
+else
+  EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lstdc++"
+fi
+
         ;;
     arm*-apple-darwin*|*-ios-*)
         ARCH=ios

configure.in

@@ -3534,7 +3534,10 @@ AC_HELP_STRING([--enable-render-d3d], [enable the Direct3D render driver [[defau
         fi
         # The Haiku platform requires special setup.
         SOURCES="$srcdir/src/main/haiku/*.cc $SOURCES"
-        EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lroot -lbe -lmedia -lgame -ldevice -ltextencoding -lstdc++.r4"
+        EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lroot -lbe -lmedia -lgame -ldevice -ltextencoding"
+        # Haiku's x86 spins use libstdc++.r4.so (for binary compat?), but
+        #  other spins, like x86-64, use a more standard "libstdc++.so.*"
+        AC_CHECK_FILE("/boot/system/lib/libstdc++.r4.so", EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lstdc++.r4", EXTRA_LDFLAGS="$EXTRA_LDFLAGS -lstdc++")
         ;;
     arm*-apple-darwin*|*-ios-*)
         ARCH=ios