Add a CMake option to disable shared libs

This option is useful to support platforms that do not support
dynamic libraries and `dlopen`.

CMakeLists.txt

@@ -287,6 +287,10 @@ option(WITH_ASYNC_EXPORT_PREVIEW "Whether to enable async export" OFF)
 option(WITH_METRICS_EXEMPLAR_PREVIEW
        "Whether to enable exemplar within metrics" OFF)
 
+option(OPENTELEMETRY_STATIC_ONLY
+       "Whether to build test libraries that are always linked as shared libs"
+       OFF)
+
 #
 # Verify options dependencies
 #

api/test/singleton/CMakeLists.txt

@@ -1,6 +1,10 @@
 # Copyright The OpenTelemetry Authors
 # SPDX-License-Identifier: Apache-2.0
 
+if(OPENTELEMETRY_STATIC_ONLY)
+  return()
+endif()
+
 include(GoogleTest)
 
 # Header only singletons are not available in windows yet.

examples/plugin/plugin/CMakeLists.txt

@@ -1,5 +1,9 @@
 # Copyright The OpenTelemetry Authors
 # SPDX-License-Identifier: Apache-2.0
 
+if(OPENTELEMETRY_STATIC_ONLY)
+  return()
+endif()
+
 add_library(example_plugin SHARED tracer.cc factory_impl.cc)
 target_link_libraries(example_plugin opentelemetry_api)