bin/hipcc: Simplify HIP_HCC_SYS_INCLUDES_WA logic

Change-Id: I2d20d6edc1b5c0d065ba6ce6179441fa98712a87


[ROCm/clr commit: 5f2bf5219a]

projects/clr/hipamd/bin/hipcc

@@ -92,8 +92,8 @@ if ($HIP_PLATFORM eq "hcc") {
     $HIPCXXFLAGS = $HCCFLAGS;
 
     #### GCC system includes workaround ####
-    $WA = $ENV{'HIP_HCC_SYS_INCLUDES_WA'};
-    if (defined($WA) and ${WA} ne "0") {
+    $WA = $ENV{'HIP_HCC_SYS_INCLUDES_WA'} // 0;
+    if (${WA}) {
         my $GCC_CUR_VER = `gcc -dumpversion`;
         my $GPP_CUR_VER = `g++ -dumpversion`;
         $GCC_CUR_VER =~ s/\R//g;