Add -Iext/opentelemetry-cpp-api-only/include for BSD

make-bsd.mk

@@ -1,6 +1,6 @@
 # This requires GNU make, which is typically "gmake" on BSD systems
 
-INCLUDES=-isystem ext -Iext/prometheus-cpp-lite-1.0/core/include -Iext/prometheus-cpp-lite-1.0/simpleapi/include
+INCLUDES=-isystem ext -Iext/prometheus-cpp-lite-1.0/core/include -Iext/prometheus-cpp-lite-1.0/simpleapi/include -Iext/opentelemetry-cpp-api-only/include
 DEFS=
 LIBS=
 

make-netbsd.mk

@@ -1,7 +1,7 @@
 CC=gcc
 CXX=g++
 
-INCLUDES=
+INCLUDES=-Iext/opentelemetry-cpp-api-only/include
 DEFS=
 LIBS=