cmake: fix curl-config --static-libs

The `curl-config --static-libs` command should not output paths like
-l/usr/lib/libssl.so, instead print the absolute path without `-l`.

This also removes the confusing message "Static linking is broken" which
was printed because curl-config --static-libs was disfunctional even
though the static libcurl.a library works properly.

Fixes curl#841

CMakeLists.txt

@@ -1142,9 +1142,7 @@ set(CURL_CA_BUNDLE          "")
 set(CURLVERSION             "${CURL_VERSION}")
 set(ENABLE_SHARED           "yes")
 if(CURL_STATICLIB)
-  # Broken: LIBCURL_LIBS below; .a lib is not built
-  message(WARNING "Static linking is broken!")
-  set(ENABLE_STATIC         "no")
+  set(ENABLE_STATIC         "yes")
 else()
   set(ENABLE_STATIC         "no")
 endif()
@@ -1153,9 +1151,12 @@ set(includedir              "\${prefix}/include")
 set(LDFLAGS                 "${CMAKE_SHARED_LINKER_FLAGS}")
 set(LIBCURL_LIBS            "")
 set(libdir                  "${CMAKE_INSTALL_PREFIX}/lib")
-# TODO CURL_LIBS also contains absolute paths which don't work with static -l...
 foreach(_lib ${CMAKE_C_IMPLICIT_LINK_LIBRARIES} ${CURL_LIBS})
-  set(LIBCURL_LIBS          "${LIBCURL_LIBS} -l${_lib}")
+  if(_lib MATCHES ".*/.*")
+    set(LIBCURL_LIBS          "${LIBCURL_LIBS} ${_lib}")
+  else()
+    set(LIBCURL_LIBS          "${LIBCURL_LIBS} -l${_lib}")
+  endif()
 endforeach()
 # "a" (Linux) or "lib" (Windows)
 string(REPLACE "." "" libext "${CMAKE_STATIC_LIBRARY_SUFFIX}")