lib: cpp: automake: ship thrift/numeric_cast.h

The `<thrift/numeric_cast.h>` header should be part of the
installed thrift artifacts since it is included by other
installed headers.

Signed-off-by: Chris Friedt <cfriedt@meta.com>
diff --git a/lib/cpp/Makefile.am b/lib/cpp/Makefile.am
index c015b0d..7512ec5 100644
--- a/lib/cpp/Makefile.am
+++ b/lib/cpp/Makefile.am
@@ -133,6 +133,7 @@
 include_thriftdir = $(includedir)/thrift
 include_thrift_HEADERS = \
                          $(top_builddir)/config.h \
+                         src/thrift/numeric_cast.h \
                          src/thrift/thrift-config.h \
                          src/thrift/thrift_export.h \
                          src/thrift/TDispatchProcessor.h \