Raise minimum required Eigen version to 3.3.4

Ubuntu 22.04 ships with Eigen 3.4.0. The MinGW workaround for -O3
related crashes has been available in Eigen since at least version
3.2.0, see https://gitlab.com/libeigen/eigen/-/commit/cc03c9d68354ea3fed03481de045c185ddc1fc49.

Change-Id: Iebfd6ed1fa55a6b0f5bd57bd920188e7b486d8cb

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f53e998..af932c6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -234,17 +234,9 @@
 
 # Eigen.
 # Eigen delivers Eigen3Config.cmake since v3.3.3
-find_package(Eigen3 3.3 REQUIRED)
+find_package(Eigen3 3.3.4 REQUIRED NO_MODULE)
 if (Eigen3_FOUND)
   message("-- Found Eigen version ${Eigen3_VERSION}: ${Eigen3_DIR}")
-  if (CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64.*|AARCH64.*)" AND
-      Eigen3_VERSION VERSION_LESS 3.3.4)
-    # As per issue #289: https://github.com/ceres-solver/ceres-solver/issues/289
-    # the bundle_adjustment_test will fail for Eigen < 3.3.4 on aarch64.
-    message(FATAL_ERROR "-- Ceres requires Eigen version >= 3.3.4 on aarch64. "
-      "Detected version of Eigen is: ${Eigen3_VERSION}.")
-  endif()
-
   if (EIGENSPARSE)
     message("-- Enabling use of Eigen as a sparse linear algebra library.")
     list(APPEND CERES_COMPILE_OPTIONS CERES_USE_EIGEN_SPARSE)
@@ -545,18 +537,6 @@
   endif (CMAKE_BUILD_TYPE STREQUAL "Debug")
 endif (NOT CMAKE_BUILD_TYPE)
 
-if (MINGW)
-  # MinGW produces code that segfaults when performing matrix multiplications
-  # in Eigen when compiled with -O3 (see [1]), as such force the use of -O2
-  # which works.
-  #
-  # [1] http://eigen.tuxfamily.org/bz/show_bug.cgi?id=556
-  message("-- MinGW detected, forcing -O2 instead of -O3 in Release for Eigen due "
-          "to a MinGW bug: http://eigen.tuxfamily.org/bz/show_bug.cgi?id=556")
-  string(REPLACE "-O3" "-O2" CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}")
-  update_cache_variable(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}")
-endif (MINGW)
-
 # After the tweaks for the compile settings, disable some warnings on MSVC.
 if (MSVC)
   # Insecure standard library functions

docs/source/installation.rst

diff --git a/docs/source/installation.rst b/docs/source/installation.rst
index 3446ddb..9747d5f 100644
--- a/docs/source/installation.rst
+++ b/docs/source/installation.rst
@@ -21,7 +21,7 @@
 - `CMake <http://www.cmake.org>`_ (**required**) 3.16 or later.
 
 - `Eigen <http://eigen.tuxfamily.org/index.php?title=Main_Page>`_
-  (**Required**) 3.3 or later.
+  (**Required**) 3.3.4 or later.
 
   .. NOTE ::
 
@@ -361,7 +361,7 @@
 #. Get dependencies; unpack them as subdirectories in ``ceres/``
    (``ceres/eigen``, ``ceres/glog``, etc.)
 
-   #. ``Eigen`` 3.3 . Configure and optionally install Eigen. It should be
+   #. ``Eigen`` 3.3.4 . Configure and optionally install Eigen. It should be
       exported into the CMake package registry by default as part of the
       configure stage so installation should not be necessary.