BUILD: Fix PSP compiler failing during C++ version tests

The blessed way to run the compiler is to use some custom GNU Make
file from PSPSDK, which we do not use, which sets the appropriate
linker flags. Running the compiler stand-alone just fails at link
time because crt0.o references libraries which are not included
by default.

The main compiler test was changed to not link
in 513cdb4, apparently because the
PS2SDK did the same thing, and now that we have more tests (some
of which do require linking since we test for unresolvable
symbols), it is really necessary to get the flags set up early.

configure

@@ -1835,6 +1835,15 @@ psp)
 		echo "Please set PSPSDK in your environment. export PSPSDK=<path to psp sdk>"
 		exit 1
 	fi
+
+	# These have to be set early because the compiler will not link successfully
+	# during testing otherwise
+	if test -d "$PSPDEV/psp/lib"; then
+		append_var LDFLAGS "-L$PSPDEV/psp/lib"
+	fi
+	append_var LDFLAGS "-L$PSPSDK/lib"
+	append_var LDFLAGS "-specs=$_srcdir/backends/platform/psp/psp.spec"
+
 	;;
 riscos)
 	if test -z "$GCCSDK_INSTALL_ENV"; then
@@ -2865,12 +2874,6 @@ case $_host_os in
 		add_line_to_config_h "#define PREFIX \"${prefix}\""
 		;;
 	psp)
-		if test -d "$PSPDEV/psp/lib"; then
-			append_var LDFLAGS "-L$PSPDEV/psp/lib"
-		fi
-		append_var LDFLAGS "-L$PSPSDK/lib"
-		append_var LDFLAGS "-specs=$_srcdir/backends/platform/psp/psp.spec"
-		_optimization_level=-O3
 		append_var CXXFLAGS "-I$PSPSDK/include"
 		# FIXME: Why is the following in CXXFLAGS and not in DEFINES? Change or document this.
 		append_var CXXFLAGS "-D_PSP_FW_VERSION=150"