Remove dependency on "curl" binary

Makefile.config.in

@@ -14,7 +14,6 @@ LIBLZMA_LIBS = @LIBLZMA_LIBS@
 SQLITE3_LIBS = @SQLITE3_LIBS@
 bash = @bash@
 bindir = @bindir@
-curl = @curl@
 datadir = @datadir@
 datarootdir = @datarootdir@
 docdir = @docdir@

configure.ac

@@ -114,7 +114,6 @@ if test -z "$$1"; then
 fi
 ])
 
-NEED_PROG(curl, curl)
 NEED_PROG(bash, bash)
 NEED_PROG(patch, patch)
 AC_PATH_PROG(xmllint, xmllint, false)

src/nix-store/local.mk

@@ -7,5 +7,3 @@ nix-store_SOURCES := $(wildcard $(d)/*.cc)
 nix-store_LIBS = libmain libstore libutil libformat
 
 nix-store_LDFLAGS = -lbz2 -pthread $(SODIUM_LIBS)
-
-nix-store_CXXFLAGS = -DCURL=\"$(curl)\"