HAVE_RULES support for build.bat

Let the user's setting of the HAVE_RULES environment variable
affect build.bat's calls to qmake.

build-pcre.txt

@@ -14,8 +14,7 @@ If you're using qmake to generate makefiles, the following behavior applies:
     by passing HAVE_RULES=yes to qmake.
 
     - Note: This includes using build.bat since it calls qmake - to use PCRE and
-        build.bat, you need to edit build.bat to add HAVE_RULES=yes to the
+        build.bat, you need to run set HAVE_RULES=yes before each run of build.bat
-        qmake call.
 
 
 Some temporary build instructions. This is work in progress.

build.bat

@@ -7,6 +7,9 @@ REM  where <target> is any of cppcheck/gui/tests/all
 REM        release or debug is the configuration
 REM  all-target builds both cppcheck and gui.
 REM
+REM Run the command before build.bat to enable rules using pcre:
+REM   set HAVE_RULES=yes
+REM
 REM TODO:
 REM  - run tests too
 
@@ -31,7 +34,7 @@ goto help
 
 :cppcheck
 cd cli
-qmake -config %TARGET%
+qmake -config %TARGET% HAVE_RULES=%HAVE_RULES%
 %MAKE%
 cd ..
 if "%1" == "all" goto gui
@@ -39,7 +42,7 @@ goto end
 
 :gui
 cd gui
-qmake -config %TARGET%
+qmake -config %TARGET% HAVE_RULES=%HAVE_RULES%
 %MAKE%
 lrelease gui.pro
 cd ..
@@ -47,7 +50,7 @@ goto end
 
 :tests
 cd test
-qmake -config %TARGET%
+qmake -config %TARGET% HAVE_RULES=%HAVE_RULES%
 %MAKE%
 cd ..
 goto end