dev-libs/re2 is built with a Makefile which doesn't install any cmake modules.
For now, use pkgconfig.

Bug: https://bugs.gentoo.org/940734
Signed-off-by: Peter Levine <plevine457@gmail.com>

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,7 +25,9 @@
     find_package(absl REQUIRED)
   endif()
   if(NOT TARGET re2::re2)
-    find_package(re2 REQUIRED)
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(re2 REQUIRED IMPORTED_TARGET re2)
+    add_library(re2::re2 ALIAS PkgConfig::re2)
   endif()
 endif()
 
--- a/googletest/cmake/Config.cmake.in
+++ b/googletest/cmake/Config.cmake.in
@@ -6,7 +6,9 @@
 endif()
 if (@GTEST_HAS_ABSL@)
   find_dependency(absl)
-  find_dependency(re2)
+  find_package(PkgConfig)
+  pkg_check_modules(re2 IMPORTED_TARGET re2)
+  add_library(re2::re2 ALIAS PkgConfig::re2)
 endif()
 
 include("${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake")