[CMake] Add option to enable pcre

Closes #2031, #2065.

CHANGES.current

@@ -7,6 +7,9 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2021-10-03: jschueller
+            [CMake] #2065: Add option to enable or disable PCRE support.
+
 2021-09-16: ianlancetaylor
             [Go] Improved _cgo_panic implementation.
 

CMakeLists.txt

@@ -73,9 +73,9 @@ if (MSVC)
   set (CMAKE_CXX_FLAGS "/EHsc ${CMAKE_CXX_FLAGS}")
 endif ()
 
-set (PCRE_REQUIRED_ARG "REQUIRED" CACHE STRING "required arg")
-find_package (PCRE ${PCRE_REQUIRED_ARG})
-if (PCRE_FOUND)
+option (WITH_PCRE "Enable pcre" ON)
+if (WITH_PCRE)
+  find_package (PCRE REQUIRED)
   set (HAVE_PCRE 1)
   include_directories (${PCRE_INCLUDE_DIRS})
 endif()

Doc/Manual/Windows.html

@@ -251,7 +251,8 @@ For fully working build steps always check the Continuous Integration setups cur
         and save to a folder e.g. C:\Tools\Bison
     </li>
     <li>
-        Install PCRE using Nuget using the following command: <pre>C:\Tools\nuget install pcre -Version 8.33.0.1 -OutputDirectory C:\Tools\pcre</pre>
+        Install PCRE using Nuget using the following command: <pre>C:\Tools\nuget install pcre -Version 8.33.0.1 -OutputDirectory C:\Tools\pcre</pre>.
+        Alternatively, use <tt>WITH_PCRE</tt> option to disable PCRE support if you are sure not to need it.
     </li>
     <li>
         We will also need the SWIG source code. Either download a zipped archive from GitHub, or if git is installed clone the latest codebase