all: switch to LLVM 16

This commit adds support for LLVM 16 and switches to it by default. That
means three LLVM versions are supported at the same time: LLVM 14, 15,
and 16.

This commit includes work by QuLogic:

  * Part of this work was based on a PR by QuLogic:
    https://github.com/tinygo-org/tinygo/pull/3649
    But I also had parts of this already implemented in an old branch I
    already made for LLVM 16.
  * QuLogic also provided a CGo fix here, which is also incorporated in
    this commit:
    https://github.com/tinygo-org/tinygo/pull/3869

The difference with the original PR by QuLogic is that this commit is
more complete:
  * It switches to LLVM 16 by default.
  * It updates some things to also make it work with a self-built LLVM.
  * It fixes the CGo bug in a slightly different way, and also fixes
    another one not included in the original PR.
  * It does not keep compiler tests passing on older LLVM versions. I
    have found this to be quite burdensome and therefore don't generally
    do this - the smoke tests should hopefully catch most regressions.

Makefile

@@ -10,7 +10,7 @@ LLD_SRC ?= $(LLVM_PROJECTDIR)/lld
 
 # Try to autodetect LLVM build tools.
 # Versions are listed here in descending priority order.
-LLVM_VERSIONS = 15 14 13 12 11
+LLVM_VERSIONS = 16 15 14 13 12 11
 errifempty = $(if $(1),$(1),$(error $(2)))
 detect = $(shell which $(call errifempty,$(firstword $(foreach p,$(2),$(shell command -v $(p) 2> /dev/null && echo $(p)))),failed to locate $(1) at any of: $(2)))
 toolSearchPathsVersion = $(1)-$(2)
@@ -113,7 +113,7 @@ endif
 
 .PHONY: all tinygo test $(LLVM_BUILDDIR) llvm-source clean fmt gen-device gen-device-nrf gen-device-nxp gen-device-avr gen-device-rp
 
-LLVM_COMPONENTS = all-targets analysis asmparser asmprinter bitreader bitwriter codegen core coroutines coverage debuginfodwarf debuginfopdb executionengine frontendopenmp instrumentation interpreter ipo irreader libdriver linker lto mc mcjit objcarcopts option profiledata scalaropts support target windowsdriver windowsmanifest
+LLVM_COMPONENTS = all-targets analysis asmparser asmprinter bitreader bitwriter codegen core coroutines coverage debuginfodwarf debuginfopdb executionengine frontendhlsl frontendopenmp instrumentation interpreter ipo irreader libdriver linker lto mc mcjit objcarcopts option profiledata scalaropts support target windowsdriver windowsmanifest
 
 ifeq ($(OS),Windows_NT)
     EXE = .exe
@@ -154,7 +154,7 @@ LLD_LIB_NAMES = lldCOFF lldCommon lldELF lldMachO lldMinGW lldWasm
 LLD_LIBS = $(START_GROUP) $(addprefix -l,$(LLD_LIB_NAMES)) $(END_GROUP)
 
 # Other libraries that are needed to link TinyGo.
-EXTRA_LIB_NAMES = LLVMInterpreter LLVMMCA LLVMX86TargetMCA
+EXTRA_LIB_NAMES = LLVMInterpreter LLVMMCA LLVMRISCVTargetMCA LLVMX86TargetMCA
 
 # All libraries to be built and linked with the tinygo binary (lib/lib*.a).
 LIB_NAMES = clang $(CLANG_LIB_NAMES) $(LLD_LIB_NAMES) $(EXTRA_LIB_NAMES)
@@ -170,7 +170,7 @@ NINJA_BUILD_TARGETS = clang llvm-config llvm-ar llvm-nm $(addprefix lib/lib,$(ad
 # For static linking.
 ifneq ("$(wildcard $(LLVM_BUILDDIR)/bin/llvm-config*)","")
     CGO_CPPFLAGS+=$(shell $(LLVM_CONFIG_PREFIX) $(LLVM_BUILDDIR)/bin/llvm-config --cppflags) -I$(abspath $(LLVM_BUILDDIR))/tools/clang/include -I$(abspath $(CLANG_SRC))/include -I$(abspath $(LLD_SRC))/include
-    CGO_CXXFLAGS=-std=c++14
+    CGO_CXXFLAGS=-std=c++17
     CGO_LDFLAGS+=-L$(abspath $(LLVM_BUILDDIR)/lib) -lclang $(CLANG_LIBS) $(LLD_LIBS) $(shell $(LLVM_CONFIG_PREFIX) $(LLVM_BUILDDIR)/bin/llvm-config --ldflags --libs --system-libs $(LLVM_COMPONENTS)) -lstdc++ $(CGO_LDFLAGS_EXTRA)
 endif
 
@@ -238,7 +238,7 @@ gen-device-renesas: build/gen-device-svd
 
 # Get LLVM sources.
 $(LLVM_PROJECTDIR)/llvm:
-	git clone -b xtensa_release_15.x --depth=1 https://github.com/espressif/llvm-project $(LLVM_PROJECTDIR)
+	git clone -b xtensa_release_16.x --depth=1 https://github.com/espressif/llvm-project $(LLVM_PROJECTDIR)
 llvm-source: $(LLVM_PROJECTDIR)/llvm
 
 # Configure LLVM.