make: Precompiled: add rules for picolib

Author: bradjc

Precompiled.mk

@@ -60,6 +60,39 @@ $(foreach arch,$(RISCV_ARCHS),$(eval $(call PRECOMPILED_NEWLIB_RULES,riscv,riscv
 $(TOCK_NEWLIB_TARGETS):
 	cd $(TOCK_USERLAND_BASE_DIR)/lib; ./fetch-newlib.sh $(patsubst libtock-newlib-%,%,$*)
 
+################################################################################
+# Picolib Rules
+#
+# These pre-compiled archives were created using the libtock-c/picolib folder.
+################################################################################
+
+# Rule to ensure that the picolib libraries for an architecture exist.
+#
+# Need to list all libraries which are possible targets to tell make that one
+# invocation of this build rule will make all the target files.
+#
+# Arguments:
+# - $(1): Family
+# - $(2): Toolchain
+# - $(3): Arch
+define PRECOMPILED_PICOLIB_RULES
+
+TOCK_PICOLIB_TARGETS += $$(TOCK_USERLAND_BASE_DIR)/lib/%/$(1)/$(2)/lib/$(3)/libc.a
+TOCK_PICOLIB_TARGETS += $$(TOCK_USERLAND_BASE_DIR)/lib/%/$(1)/$(2)/lib/$(3)/libm.a
+
+endef
+
+TOCK_PICOLIB_TARGETS :=
+$(foreach arch,$(ARM_ARCHS),$(eval $(call PRECOMPILED_PICOLIB_RULES,arm,arm-none-eabi,$(arch))))
+$(foreach arch,$(RISCV_ARCHS),$(eval $(call PRECOMPILED_PICOLIB_RULES,riscv,riscv64-unknown-elf,$(arch))))
+
+# Target to download and extract picolib.
+#
+# % will match something like "libtock-picolib-1.8.5" which we then strip down
+# to just the version with some string manipulation.
+$(TOCK_PICOLIB_TARGETS):
+	cd $(TOCK_USERLAND_BASE_DIR)/lib; ./fetch-picolib.sh $(patsubst libtock-picolib-%,%,$*)
+
 ################################################################################
 # LIBC++ Rules
 #
@@ -75,7 +108,7 @@ TOCK_CXXLIB_TARGETS += $$(TOCK_USERLAND_BASE_DIR)/lib/%/$(1)/$(2)/lib/$(3)/libsu
 # So this is supremely frustrating. The issue boils down to limitations of
 # pattern rules in make.
 #
-# First: pattern rules are implicitly groups, and you aren't allowed to 
+# First: pattern rules are implicitly groups, and you aren't allowed to
 # use the :g operator to merge groups. What this means in practice is that
 # if you have many targets that are all generated by the same rule (i.e.,
 # our unzip creates all the library archive targets), all of the targets