build: improve man page installation

man pages are extremely useful, but are not generally available on
Windows.  This changes the install condition to check for the Windows
cross-compile rather than the toolchain in use.  It is possible to build
for Windows using clang in the GNU driver.

Author: compnerd

CMakeLists.txt

@@ -39,7 +39,11 @@ endif()
 
 add_subdirectory(src)
 add_subdirectory(extensions)
-add_subdirectory(man)
+# TODO(compnerd) should this be enabled for MinGW, which sets CMAKE_SYSTEM_NAME
+# to Windows, but defines `MINGW`.
+if(NOT CMAKE_SYSTEM_NAME STREQUAL Windows)
+  add_subdirectory(man)
+endif()
 if(BUILD_TESTING)
   add_subdirectory(test testdir)
   if(CMARK_STATIC OR CMARK_SHARED)

man/CMakeLists.txt

@@ -1,7 +1,4 @@
-if (NOT MSVC)
-  install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/man1/cmark-gfm.1
-    DESTINATION ${CMAKE_INSTALL_MANDIR}/man1)
-
-  install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/man3/cmark-gfm.3
-    DESTINATION ${CMAKE_INSTALL_MANDIR}/man3)
-endif(NOT MSVC)
+install(FILES man1/cmark-gfm.1
+  DESTINATION ${CMAKE_INSTALL_MANDIR}/man1)
+install(FILES man3/cmark-gfm.3
+  DESTINATION ${CMAKE_INSTALL_MANDIR}/man3)