build: re-add support for legacy SystemC installations

cmake/FindSystemC.cmake

@@ -0,0 +1,46 @@
+# User must provide SYSTEMC_HOME
+# Defines:
+#   SystemC_FOUND
+#   SystemC_INCLUDE_DIRS
+#   SystemC_LIBRARIES
+#   SystemC_VERSION (optional)
+#   SystemC::systemc (imported target)
+
+if (NOT DEFINED SYSTEMC_HOME)
+    message(FATAL_ERROR "SYSTEMC_HOME is not defined. Please set it to your SystemC installation directory.")
+endif()
+
+find_library(SystemC_LIBRARY
+    NAMES systemc systemc-ar
+    HINTS ${SYSTEMC_HOME}
+    PATH_SUFFIXES
+        lib
+        lib64
+        lib-linux
+        lib-linux64
+        lib-macos
+    NO_DEFAULT_PATH
+)
+
+if (NOT SystemC_LIBRARY)
+    message(FATAL_ERROR "SystemC library not found in ${SYSTEMC_HOME}")
+endif()
+
+set(SystemC_VERSION "")
+set(SystemC_INCLUDE_DIR "${SYSTEMC_HOME}/include")
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(SystemC
+    REQUIRED_VARS SystemC_LIBRARY SystemC_INCLUDE_DIR
+    VERSION_VAR SystemC_VERSION
+)
+
+mark_as_advanced(SystemC_INCLUDE_DIR SystemC_LIBRARY)
+
+if (SystemC_FOUND)
+    add_library(SystemC::systemc UNKNOWN IMPORTED)
+    set_target_properties(SystemC::systemc PROPERTIES
+        IMPORTED_LOCATION "${SystemC_LIBRARY}"
+        INTERFACE_INCLUDE_DIRECTORIES "${SystemC_INCLUDE_DIR}"
+    )
+endif()