https://bugs.gentoo.org/827173
https://sources.debian.org/patches/htp/1.19-8/0004-Parallel-ftbfs.patch/

Description: Fix occasional parallel FTBFS
 Various source files indirectly include $(d)/version.inc,
 don't regenerate it in the middle of the build.
Author: Adrian Bunk <bunk@debian.org>

--- htp-1.19.orig/src/Makefile.sub
+++ htp-1.19/src/Makefile.sub
@@ -57,14 +57,12 @@ $(HTP) : $(OBJ$(d))
 #
 # implicit dependencies for source code
 #
-$(OBJ$(d)) : %.$(OBJEXT) : %.c
+$(OBJ$(d)) : %.$(OBJEXT) : %.c $(d)/version.inc
 ifdef WIN32DMC
 	cd $(dir $<); $(CC) $(CCOPT) $(DEFINES) $(notdir $<)
 else
 	$(CC) $(CCOPT) $(DEFINES) -o $*.$(OBJEXT) $<
 endif
 
-$(d)/htp.$(OBJEXT) $(d)/ver.$(OBJEXT): $(d)/version.inc
-
 # restore parent dir
 d := $(p$(d))