[UNIKRAFT PATCH 4/7] build: Pre-processing rule for AWK progfiles

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

Introduces an AWK pre-processing rule as another way for generating source
files based on AWK progfiles. One intention of this is to simplify
`Makefile.uk` of `lib/syscall_shim`.
The source file is treated as the AWK progfile which will be executed over
given includes (`AWKINCLUDES[-y]`). Because global flags and includes
would not be meaningful for AWK rules, we support only library-local and
file-local scopes.

Example of compiling `uk_syscall6.o` from `uk_syscall6.awk`
in `lib/syscall_shim`:
 LIBSYSCALL_SHIM_SRCS += $(LIBSYSCALL_SHIM_BASE)/gen_uk_syscall6.awk>.c
 LIBSYSCALL_SHIM_GEN_UK_SYSCALL6_AWKFLAGS    += -F '-'
 LIBSYSCALL_SHIM_GEN_UK_SYSCALL6_AWKINCLUDES += 
$(LIBSYSCALL_SHIM_BUILD)/provided_syscalls.h.in

Signed-off-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
---
 support/build/Makefile.rules | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/support/build/Makefile.rules b/support/build/Makefile.rules
index 6a8c2099..e1c078c3 100644
--- a/support/build/Makefile.rules
+++ b/support/build/Makefile.rules
@@ -634,6 +634,30 @@ UK_SRCS-y += $(2)
 $(eval $(call vprefix_lib,$(1),CLEAN-y) += $(call build_clean,$(3)))
 endef
 
+# Pre-processing rule for awk progs
+# NOTES:
+#  $source is the awk progfile and AWKINCLUDES specify the input files to
+#  process. There are no global scopes for AWKINCLUDES and AWKFLAGS available
+#  because it would not be meaningful.
+define preprule_awk =
+$(3): $(2) \
+      $$($(call vprefix_lib,$(1),AWKINCLUDES)) $$($(call 
vprefix_lib,$(1),AWKINCLUDES-y)) \
+      $$($(call vprefix_src,$(1),$(2),,AWKINCLUDES)) $$($(call 
vprefix_src,$(1),$(2),,AWKINCLUDES-y)) \
+      | prepare
+       $(call build_cmd,AWK,$(1),$(3),\
+               $(AWK) -f $(2) \
+                      $$($(call vprefix_lib,$(1),AWKFLAGS)) $$($(call 
vprefix_lib,$(1),AWKFLAGS-y)) \
+                      $$($(call vprefix_src,$(1),$(2),,AWKFLAGS)) $$($(call 
vprefix_src,$(1),$(2),,AWKFLAGS-y)) \
+                      $(4) \
+                      $$($(call vprefix_lib,$(1),AWKINCLUDES)) $$($(call 
vprefix_lib,$(1),AWKINCLUDES-y)) \
+                      $$($(call vprefix_src,$(1),$(2),,AWKINCLUDES)) $$($(call 
vprefix_src,$(1),$(2),,AWKINCLUDES-y)) \
+                      > $(3)
+       )
+
+UK_SRCS-y += $(2)
+$(eval $(call vprefix_lib,$(1),CLEAN-y) += $(call build_clean,$(3)))
+endef
+
 # wrapper for preprule_*,
 # selects appropriate pre-process rule depending on file extension
 # if there is no such pre-process rule available, we throw an error.
-- 
2.20.1