Add libdl.so to the list of system shared libs

Note that libdl is already (always) implicitly loaded
because libc.so has a dependency on it.

This change also makes sure that libc.so always goes before
libdl.so in DT_NEEDED list.

Bug: http://b/62815515
Test: make
Change-Id: Idb231f8a8443ee859828bac6462236a1b7199d05

cc/linker.go

@@ -152,11 +152,23 @@ func (linker *baseLinker) linkerDeps(ctx BaseModuleContext, deps Deps) Deps {
 		}
 
 		if !ctx.static() {
+			// libdl should always appear after libc in dt_needed list - see below
+			// the only exception is when libc is not in linker.Properties.System_shared_libs
+			// such as for libc module itself
+			if inList("libc", linker.Properties.System_shared_libs) {
+				_, deps.SharedLibs = removeFromList("libdl", deps.SharedLibs)
+			}
+
 			if linker.Properties.System_shared_libs != nil {
+				if !inList("libdl", linker.Properties.System_shared_libs) &&
+					inList("libc", linker.Properties.System_shared_libs) {
+					linker.Properties.System_shared_libs = append(linker.Properties.System_shared_libs,
+						"libdl")
+				}
 				deps.LateSharedLibs = append(deps.LateSharedLibs,
 					linker.Properties.System_shared_libs...)
 			} else if !ctx.sdk() && !ctx.vndk() {
-				deps.LateSharedLibs = append(deps.LateSharedLibs, "libc", "libm")
+				deps.LateSharedLibs = append(deps.LateSharedLibs, "libc", "libm", "libdl")
 			}
 		}
 
@@ -164,10 +176,11 @@ func (linker *baseLinker) linkerDeps(ctx BaseModuleContext, deps Deps) Deps {
 			deps.SharedLibs = append(deps.SharedLibs,
 				"libc",
 				"libm",
+				"libdl",
 			)
 		}
 		if ctx.vndk() {
-			deps.LateSharedLibs = append(deps.LateSharedLibs, "libc", "libm")
+			deps.LateSharedLibs = append(deps.LateSharedLibs, "libc", "libm", "libdl")
 		}
 	}