Remove --enable-nix-ccache

There now is a generic flake for this at
https://github.com/edolstra/nix-ccache.

Makefile.config.in

@@ -12,7 +12,6 @@ LDFLAGS = @LDFLAGS@
 LIBBROTLI_LIBS = @LIBBROTLI_LIBS@
 LIBCURL_LIBS = @LIBCURL_LIBS@
 LIBLZMA_LIBS = @LIBLZMA_LIBS@
-NIX_CCACHE = @NIX_CCACHE@
 OPENSSL_LIBS = @OPENSSL_LIBS@
 PACKAGE_NAME = @PACKAGE_NAME@
 PACKAGE_VERSION = @PACKAGE_VERSION@

configure.ac

@@ -312,18 +312,6 @@ else
 fi
 
 
-# Whether to use Nix at build time to cache compilations.
-AC_ARG_ENABLE(nix-ccache, AC_HELP_STRING([--enable-nix-ccache],
-  [Whether to use Nix at build time to cache/distribute C++ compilations [default=no]]),
-  nix_ccache=$enableval, nix_ccache=no)
-if test "$nix_ccache" = yes; then
-  NEED_PROG(nix_build, nix-build)
-  AC_SUBST(NIX_CCACHE, 1)
-else
-  AC_SUBST(NIX_CCACHE, 0)
-fi
-
-
 # Expand all variables in config.status.
 test "$prefix" = NONE && prefix=$ac_default_prefix
 test "$exec_prefix" = NONE && exec_prefix='${prefix}'

mk/patterns.mk

@@ -2,12 +2,4 @@ CXX_PATH = $(shell sh -c 'type -p $(CXX)')
 
 $(buildprefix)%.o: %.cc
 	@mkdir -p "$(dir $@)"
-ifeq ($(NIX_CCACHE), 1)
-	$(trace-cpp) $(CXX) -o $@.ii -E $< $(GLOBAL_CXXFLAGS) $(GLOBAL_CXXFLAGS_PCH) $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(call filename-to-dep, $@) -MP -MT $@
-	$(trace-cxx) $(nix_build) --quiet -o $@.link -E '(derivation { name = "cc"; system = "x86_64-linux"; builder = "/bin/sh"; args = [ "-c" "$${builtins.storePath $(CXX_PATH)} -std=c++17 -o $$out -c $${$@.ii} -g -Wall -fPIC -g -O3" ]; })' > /dev/null
-	@rm -f $@
-	@cp $@.link $@
-	@rm -f $@.ii $@.link
-else
 	$(trace-cxx) $(CXX) -o $@ -c $< $(GLOBAL_CXXFLAGS) $(GLOBAL_CXXFLAGS_PCH) $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(call filename-to-dep, $@) -MP -MT $@
-endif

mk/tracing.mk

@@ -5,7 +5,6 @@ ifeq ($(V), 0)
   trace-gen     = @echo "  GEN   " $@;
   trace-cc      = @echo "  CC    " $@;
   trace-cxx     = @echo "  CXX   " $@;
-  trace-cpp     = @echo "  CPP   " $@;
   trace-ld      = @echo "  LD    " $@;
   trace-ar      = @echo "  AR    " $@;
   trace-install = @echo "  INST  " $@;