allow install to complete even if no prebuilt man pages are available

If pandoc and rst2man are available, they are used to create man
page sources. If not, then the build looks for prebuilt man pages
in ${CMAKE_SOURCE_DIR}/buildlib/pandoc-prebuilt. If that directory
is not present (e.g. because you are compiling from a fresh checkout
of master from github), then rdma-core will compile fine but the
"make install" operation will fail.

This patch adds a new cmake cache variable NO_MAN_PAGES (default=0).
If set, it disables man page processing and allows "make install" to
succeed (without man pages) when neither pandoc/rst2man nor pandoc-prebuilt
are present.

Signed-off-by: Chuck Cranor <chuck@ece.cmu.edu>

CMakeLists.txt

@@ -48,6 +48,10 @@
 #   -DENABLE_IBDIAGS_COMPAT=True (default False)
 #      Include obsolete scripts. These scripts are replaced by C programs with
 #      a different interface now.
+#   -DNO_MAN_PAGES=1 (default 0, build/install the man pages)
+#      Disable man pages. Allows rdma-core to be built and installed
+#      (without man pages) when neither pandoc/rst2man nor the pandoc-prebuilt
+#      directory are available.
 
 cmake_minimum_required(VERSION 2.8.11 FATAL_ERROR)
 project(rdma-core C)
@@ -174,7 +178,15 @@ include(RDMA_DoFixup)
 include(publish_headers)
 include(rdma_functions)
 include(pyverbs_functions)
-include(rdma_man)
+if (NO_MAN_PAGES)
+  # define empty stub functions to omit man page processing
+  function(rdma_man_pages)
+  endfunction()
+  function(rdma_alias_man_pages)
+  endfunction()
+else()
+  include(rdma_man)
+endif()
 
 if (NOT DEFINED ENABLE_STATIC)
   set(ENABLE_STATIC "OFF" CACHE BOOL "Produce static linking libraries as well as shared libraries.")
@@ -423,9 +435,12 @@ if (CYTHON_EXECUTABLE)
   string(STRIP ${py_path} CMAKE_PYTHON_SO_SUFFIX)
 endif()
 
-# Look for pandoc and rst2man for making manual pages
-FIND_PACKAGE(pandoc)
-FIND_PACKAGE(rst2man)
+set(NO_MAN_PAGES "OFF" CACHE BOOL "Disable build/install of man pages")
+if (NOT NO_MAN_PAGES)
+  # Look for pandoc and rst2man for making manual pages
+  FIND_PACKAGE(pandoc)
+  FIND_PACKAGE(rst2man)
+endif ()
 
 #-------------------------
 # Find libraries
@@ -703,18 +718,22 @@ else()
     message(STATUS " netlink/route/link.h and net/if.h NOT co-includable (old headers)")
   endif()
 endif()
-if (NOT PANDOC_FOUND)
-  if (NOT EXISTS "${CMAKE_SOURCE_DIR}/buildlib/pandoc-prebuilt")
-    message(STATUS " pandoc NOT found and NO prebuilt man pages. 'install' disabled")
-  else()
-    message(STATUS " pandoc NOT found (using prebuilt man pages)")
+if (NO_MAN_PAGES)
+  message(STATUS " man pages NOT built")
+else()
+  if (NOT PANDOC_FOUND)
+    if (NOT EXISTS "${CMAKE_SOURCE_DIR}/buildlib/pandoc-prebuilt")
+      message(STATUS " pandoc NOT found and NO prebuilt man pages. 'install' disabled")
+    else()
+      message(STATUS " pandoc NOT found (using prebuilt man pages)")
+    endif()
   endif()
-endif()
-if (NOT RST2MAN_FOUND)
-  if (NOT EXISTS "${CMAKE_SOURCE_DIR}/buildlib/pandoc-prebuilt")
-    message(STATUS " rst2man NOT found and NO prebuilt man pages. 'install' disabled")
-  else()
-    message(STATUS " rst2man NOT found (using prebuilt man pages)")
+  if (NOT RST2MAN_FOUND)
+    if (NOT EXISTS "${CMAKE_SOURCE_DIR}/buildlib/pandoc-prebuilt")
+      message(STATUS " rst2man NOT found and NO prebuilt man pages. 'install' disabled")
+    else()
+      message(STATUS " rst2man NOT found (using prebuilt man pages)")
+    endif()
   endif()
 endif()
 if (NOT CYTHON_EXECUTABLE)