build: Refactor directory structure to separate headers

This makes the structure similar to other OpenBMC projects.

Change-Id: I5b76fe7439dba9b68244ee1494f2266b6351e498
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/include/meson.build b/include/meson.build
new file mode 100644
index 0000000..5d870ac
--- /dev/null
+++ b/include/meson.build
@@ -0,0 +1,44 @@
+stdplus_headers = include_directories('.')
+
+if has_dl
+  install_headers(
+    'stdplus/dl.hpp',
+    subdir: 'stdplus')
+endif
+
+if has_fd
+  install_headers(
+    'stdplus/fd/create.hpp',
+    'stdplus/fd/dupable.hpp',
+    'stdplus/fd/gmock.hpp',
+    'stdplus/fd/impl.hpp',
+    'stdplus/fd/intf.hpp',
+    'stdplus/fd/managed.hpp',
+    'stdplus/fd/mmap.hpp',
+    'stdplus/fd/ops.hpp',
+    subdir: 'stdplus/fd')
+endif
+
+if has_io_uring
+  install_headers(
+    'stdplus/io_uring.hpp',
+    subdir: 'stdplus')
+endif
+
+install_headers(
+  'stdplus/cancel.hpp',
+  'stdplus/exception.hpp',
+  'stdplus/flags.hpp',
+  'stdplus/raw.hpp',
+  'stdplus/signal.hpp',
+  subdir: 'stdplus')
+
+install_headers(
+  'stdplus/handle/copyable.hpp',
+  'stdplus/handle/managed.hpp',
+  subdir: 'stdplus/handle')
+
+install_headers(
+  'stdplus/util/cexec.hpp',
+  'stdplus/util/string.hpp',
+  subdir: 'stdplus/util')