depends: Use vendored Clang for native compilation

Clang is used for compiling C/C++ dependencies, as well as the Zcash
binaries themselves. GCC is still required for compiling native
toolchain dependencies (such as ccache).

depends/hosts/default.mk

@@ -1,12 +1,22 @@
-default_host_CC = $(host_toolchain)gcc
-default_host_CXX = $(host_toolchain)g++
-default_host_AR = $(host_toolchain)ar
-default_host_RANLIB = $(host_toolchain)ranlib
-default_host_STRIP = $(host_toolchain)strip
+# Flag explanations:
+#
+#     -B$(build_prefix)/bin
+#
+#         Explicitly point to our binaries (e.g. cctools) so that they are
+#         ensured to be found and preferred over other possibilities.
+#
+default_host_CC = clang -target $(host) -B$(build_prefix)/bin
+default_host_CXX = clang++ -target $(host) -B$(build_prefix)/bin -stdlib=libc++
+default_host_AR = llvm-ar
+default_host_RANLIB = llvm-ranlib
+default_host_STRIP = llvm-strip
 default_host_LIBTOOL = $(host_toolchain)libtool
 default_host_INSTALL_NAME_TOOL = $(host_toolchain)install_name_tool
 default_host_OTOOL = $(host_toolchain)otool
-default_host_NM = $(host_toolchain)nm
+default_host_NM = llvm-nm
+
+$(host_os)_native_binutils?=native_clang
+$(host_os)_native_toolchain?=native_clang
 
 define add_host_tool_func
 $(host_os)_$1?=$$(default_host_$1)

depends/hosts/freebsd.mk

@@ -9,23 +9,7 @@ freebsd_debug_CXXFLAGS=$(freebsd_debug_CFLAGS)
 
 freebsd_debug_CPPFLAGS=-D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC
 
-ifeq (86,$(findstring 86,$(build_arch)))
-i686_freebsd_CC=gcc -m32
-i686_freebsd_CXX=g++ -m32
-i686_freebsd_AR=ar
-i686_freebsd_RANLIB=ranlib
-i686_freebsd_NM=nm
-i686_freebsd_STRIP=strip
-
-x86_64_freebsd_CC=gcc -m64
-x86_64_freebsd_CXX=g++ -m64
-x86_64_freebsd_AR=ar
-x86_64_freebsd_RANLIB=ranlib
-x86_64_freebsd_NM=nm
-x86_64_freebsd_STRIP=strip
-else
 i686_freebsd_CC=$(default_host_CC) -m32
 i686_freebsd_CXX=$(default_host_CXX) -m32
 x86_64_freebsd_CC=$(default_host_CC) -m64
 x86_64_freebsd_CXX=$(default_host_CXX) -m64
-endif

depends/hosts/linux.mk

@@ -9,23 +9,7 @@ linux_debug_CXXFLAGS=$(linux_debug_CFLAGS)
 
 linux_debug_CPPFLAGS=-D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC
 
-ifeq (86,$(findstring 86,$(build_arch)))
-i686_linux_CC=gcc -m32
-i686_linux_CXX=g++ -m32
-i686_linux_AR=ar
-i686_linux_RANLIB=ranlib
-i686_linux_NM=nm
-i686_linux_STRIP=strip
-
-x86_64_linux_CC=gcc -m64
-x86_64_linux_CXX=g++ -m64
-x86_64_linux_AR=ar
-x86_64_linux_RANLIB=ranlib
-x86_64_linux_NM=nm
-x86_64_linux_STRIP=strip
-else
 i686_linux_CC=$(default_host_CC) -m32
 i686_linux_CXX=$(default_host_CXX) -m32
 x86_64_linux_CC=$(default_host_CC) -m64
 x86_64_linux_CXX=$(default_host_CXX) -m64
-endif

depends/packages/boost.mk

@@ -16,7 +16,7 @@ $(package)_config_opts_mingw32=binary-format=pe target-os=windows threadapi=win3
 $(package)_config_opts_x86_64_mingw32=address-model=64
 $(package)_config_opts_i686_mingw32=address-model=32
 $(package)_config_opts_i686_linux=address-model=32 architecture=x86
-$(package)_toolset_$(host_os)=gcc
+$(package)_toolset_$(host_os)=clang
 $(package)_archiver_$(host_os)=$($(package)_ar)
 $(package)_toolset_darwin=darwin
 $(package)_archiver_darwin=$($(package)_libtool)