Automagical inclusion of headers from vendor libraries, in most cases

require-ess/tools/driver.makefile

@@ -659,6 +659,9 @@ USR_DBDFLAGS += $(DBDEXPANDPATH)
 # Search all directories where sources or headers come from, plus existing os dependend subdirectories.
 SRC_INCLUDES = $(addprefix -I, $(wildcard $(foreach d,$(call uniq, $(filter-out /%,$(dir ${SRCS:%=../%} ${HDRS:%=../%}))), $d $(addprefix $d/, os/${OS_CLASS} $(POSIX_$(POSIX)) os/default))))
 
+# Look for includes from standard locations relative to vendor libraries
+USR_INCLUDES += $(addprefix -I,$(wildcard $(patsubst %/lib/$(T_A)/,../%/include,$(call uniq,$(dir $(VLIBS))) $(patsubst %/lib/,../%/include,$(call uniq,$(dir $(VLIBS)))))))
+
 # Different macro name for 3.14.8.
 GENERIC_SRC_INCLUDES = $(SRC_INCLUDES)