build: split source and header directories

Split the headers and source to simplify the install_header
directive such that we no longer need to specify cpp files
to exclude in the install_header call.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Iac4c38f95e690aa8ef8ecf87b032f55a1a31409c
diff --git a/src/server/transaction.cpp b/src/server/transaction.cpp
new file mode 100644
index 0000000..2a9697f
--- /dev/null
+++ b/src/server/transaction.cpp
@@ -0,0 +1,18 @@
+#include "sdbusplus/server/transaction.hpp"
+
+namespace sdbusplus
+{
+namespace server
+{
+namespace transaction
+{
+namespace details
+{
+
+// Transaction Id
+thread_local uint64_t id = 0;
+
+} // namespace details
+} // namespace transaction
+} // namespace server
+} // namespace sdbusplus