Fix CMake path for INSTALL_INCLUDEDIR (#723)

CMake/AbseilInstallDirs.cmake

@@ -10,11 +10,11 @@ if(absl_VERSION)
   set(ABSL_SUBDIR "${PROJECT_NAME}_${PROJECT_VERSION}")
   set(ABSL_INSTALL_BINDIR "${CMAKE_INSTALL_BINDIR}/${ABSL_SUBDIR}")
   set(ABSL_INSTALL_CONFIGDIR "${CMAKE_INSTALL_LIBDIR}/cmake/${ABSL_SUBDIR}")
-  set(ABSL_INSTALL_INCLUDEDIR "${CMAKE_INSTALL_INCLUDEDIR}/{ABSL_SUBDIR}")
+  set(ABSL_INSTALL_INCLUDEDIR "${CMAKE_INSTALL_INCLUDEDIR}/${ABSL_SUBDIR}")
   set(ABSL_INSTALL_LIBDIR "${CMAKE_INSTALL_LIBDIR}/${ABSL_SUBDIR}")
 else()
   set(ABSL_INSTALL_BINDIR "${CMAKE_INSTALL_BINDIR}")
   set(ABSL_INSTALL_CONFIGDIR "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
   set(ABSL_INSTALL_INCLUDEDIR "${CMAKE_INSTALL_INCLUDEDIR}")
   set(ABSL_INSTALL_LIBDIR "${CMAKE_INSTALL_LIBDIR}")
-endif()
+endif()