Only link CURL when building Phobos as shared library.

runtime/CMakeLists.txt

@@ -97,10 +97,11 @@ list(APPEND CORE_D ${LDC_D} ${RUNTIME_DIR}/src/object_.d)
 file(GLOB CORE_C ${RUNTIME_DIR}/src/core/stdc/*.c)
 
 if(PHOBOS2_DIR)
-    #
-    # Locate curl.
-    #
-    find_package(CURL REQUIRED)
+    if(BUILD_SHARED_LIBS)
+        # std.net.curl depends on libcurl – when building a shared library, we
+        # need to take care of that.
+        find_package(CURL REQUIRED)
+    endif()
 
     file(GLOB PHOBOS2_D ${PHOBOS2_DIR}/std/*.d)
     file(GLOB PHOBOS2_D_NET ${PHOBOS2_DIR}/std/net/*.d)
@@ -352,7 +353,9 @@ macro(build_runtime d_flags c_flags ld_flags lib_suffix path_suffix)
             LINK_FLAGS                  "${ld_flags}"
         )
         # Phobos now uses curl
-        target_link_libraries(phobos-ldc${target_suffix} "curl")
+        if(BUILD_SHARED_LIBS)
+            target_link_libraries(phobos-ldc${target_suffix} "curl")
+        endif()
         install(TARGETS phobos-ldc${target_suffix} DESTINATION ${CMAKE_INSTALL_PREFIX}/lib${path_suffix})
         add_dependencies(phobos2 DEPENDS phobos-ldc${target_suffix})
     endif(PHOBOS2_DIR)