cmake: Import FindALSA from upstream CMake

CMakeTests/FindALSA.cmake

@@ -0,0 +1,52 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#.rst:
+# FindALSA
+# --------
+#
+# Find alsa
+#
+# Find the alsa libraries (asound)
+#
+# ::
+#
+#   This module defines the following variables:
+#      ALSA_FOUND       - True if ALSA_INCLUDE_DIR & ALSA_LIBRARY are found
+#      ALSA_LIBRARIES   - Set when ALSA_LIBRARY is found
+#      ALSA_INCLUDE_DIRS - Set when ALSA_INCLUDE_DIR is found
+#
+#
+#
+# ::
+#
+#      ALSA_INCLUDE_DIR - where to find asoundlib.h, etc.
+#      ALSA_LIBRARY     - the asound library
+#      ALSA_VERSION_STRING - the version of alsa found (since CMake 2.8.8)
+
+find_path(ALSA_INCLUDE_DIR NAMES alsa/asoundlib.h
+          DOC "The ALSA (asound) include directory"
+)
+
+find_library(ALSA_LIBRARY NAMES asound
+          DOC "The ALSA (asound) library"
+)
+
+if(ALSA_INCLUDE_DIR AND EXISTS "${ALSA_INCLUDE_DIR}/alsa/version.h")
+  file(STRINGS "${ALSA_INCLUDE_DIR}/alsa/version.h" alsa_version_str REGEX "^#define[\t ]+SND_LIB_VERSION_STR[\t ]+\".*\"")
+
+  string(REGEX REPLACE "^.*SND_LIB_VERSION_STR[\t ]+\"([^\"]*)\".*$" "\\1" ALSA_VERSION_STRING "${alsa_version_str}")
+  unset(alsa_version_str)
+endif()
+
+include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(ALSA
+                                  REQUIRED_VARS ALSA_LIBRARY ALSA_INCLUDE_DIR
+                                  VERSION_VAR ALSA_VERSION_STRING)
+
+if(ALSA_FOUND)
+  set( ALSA_LIBRARIES ${ALSA_LIBRARY} )
+  set( ALSA_INCLUDE_DIRS ${ALSA_INCLUDE_DIR} )
+endif()
+
+mark_as_advanced(ALSA_INCLUDE_DIR ALSA_LIBRARY)