Add .cmake files and fix LICENSE file path in make_sdist.sh.

Also make minor modifications to Python bindings code for GCC compatibility.

Fixes #191.

PiperOrigin-RevId: 435127640
Change-Id: I8bd3a35bbb2724a24341072ba8df3da4372f83d3

cmake/MujocoLinkOptions.cmake

@@ -0,0 +1,67 @@
+# Copyright 2021 DeepMind Technologies Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+include(CheckCSourceCompiles)
+
+# Gets the appropriate linker options for building MuJoCo, based on features available on the
+# linker.
+function(get_mujoco_extra_link_options OUTPUT_VAR)
+  if(MSVC)
+    set(EXTRA_LINK_OPTIONS /OPT:REF /OPT:ICF=5)
+  else()
+    set(EXTRA_LINK_OPTIONS)
+
+    if(WIN32)
+      set(CMAKE_REQUIRED_FLAGS "-fuse-ld=lld-link")
+      check_c_source_compiles("int main() {}" SUPPORTS_LLD)
+      if(SUPPORTS_LLD)
+        set(EXTRA_LINK_OPTIONS
+            ${EXTRA_LINK_OPTIONS}
+            -fuse-ld=lld-link
+            -Wl,/OPT:REF
+            -Wl,/OPT:ICF
+        )
+      endif()
+    else()
+      set(CMAKE_REQUIRED_FLAGS "-fuse-ld=lld")
+      check_c_source_compiles("int main() {}" SUPPORTS_LLD)
+      if(SUPPORTS_LLD)
+        set(EXTRA_LINK_OPTIONS ${EXTRA_LINK_OPTIONS} -fuse-ld=lld)
+      else()
+        set(CMAKE_REQUIRED_FLAGS "-fuse-ld=gold")
+        check_c_source_compiles("int main() {}" SUPPORTS_GOLD)
+        if(SUPPORTS_GOLD)
+          set(EXTRA_LINK_OPTIONS ${EXTRA_LINK_OPTIONS} -fuse-ld=gold)
+        endif()
+      endif()
+
+      set(CMAKE_REQUIRED_FLAGS ${EXTRA_LINK_OPTIONS} "-Wl,--gc-sections")
+      check_c_source_compiles("int main() {}" SUPPORTS_GC_SECTIONS)
+      if(SUPPORTS_GC_SECTIONS)
+        set(EXTRA_LINK_OPTIONS ${EXTRA_LINK_OPTIONS} -Wl,--gc-sections)
+      else()
+        set(CMAKE_REQUIRED_FLAGS ${EXTRA_LINK_OPTIONS} "-Wl,-dead_strip")
+        check_c_source_compiles("int main() {}" SUPPORTS_DEAD_STRIP)
+        if(SUPPORTS_DEAD_STRIP)
+          set(EXTRA_LINK_OPTIONS ${EXTRA_LINK_OPTIONS} -Wl,-dead_strip)
+        endif()
+      endif()
+    endif()
+  endif()
+
+  set("${OUTPUT_VAR}"
+      ${EXTRA_LINK_OPTIONS}
+      PARENT_SCOPE
+  )
+endfunction()