configure: Check for libgit2

Makefile.config.in

@@ -8,7 +8,9 @@ CXX = @CXX@
 CXXFLAGS = @CXXFLAGS@
 CXXLTO = @CXXLTO@
 EDITLINE_LIBS = @EDITLINE_LIBS@
+ENABLE_BUILD = @ENABLE_BUILD@
 ENABLE_S3 = @ENABLE_S3@
+ENABLE_TESTS = @ENABLE_TESTS@
 GTEST_LIBS = @GTEST_LIBS@
 HAVE_LIBCPUID = @HAVE_LIBCPUID@
 HAVE_SECCOMP = @HAVE_SECCOMP@
@@ -17,6 +19,7 @@ LDFLAGS = @LDFLAGS@
 LIBARCHIVE_LIBS = @LIBARCHIVE_LIBS@
 LIBBROTLI_LIBS = @LIBBROTLI_LIBS@
 LIBCURL_LIBS = @LIBCURL_LIBS@
+LIBGIT2_LIBS = @LIBGIT2_LIBS@
 LIBSECCOMP_LIBS = @LIBSECCOMP_LIBS@
 LOWDOWN_LIBS = @LOWDOWN_LIBS@
 OPENSSL_LIBS = @OPENSSL_LIBS@
@@ -35,6 +38,7 @@ docdir = @docdir@
 embedded_sandbox_shell = @embedded_sandbox_shell@
 exec_prefix = @exec_prefix@
 includedir = @includedir@
+internal_api_docs = @internal_api_docs@
 libdir = @libdir@
 libexecdir = @libexecdir@
 localstatedir = @localstatedir@
@@ -46,6 +50,3 @@ sandbox_shell = @sandbox_shell@
 storedir = @storedir@
 sysconfdir = @sysconfdir@
 system = @system@
-ENABLE_BUILD = @ENABLE_BUILD@
-ENABLE_TESTS = @ENABLE_TESTS@
-internal_api_docs = @internal_api_docs@

configure.ac

@@ -335,9 +335,15 @@ AC_ARG_ENABLE(doc-gen, AS_HELP_STRING([--disable-doc-gen],[disable documentation
   doc_generate=$enableval, doc_generate=yes)
 AC_SUBST(doc_generate)
 
+
 # Look for lowdown library.
 PKG_CHECK_MODULES([LOWDOWN], [lowdown >= 0.9.0], [CXXFLAGS="$LOWDOWN_CFLAGS $CXXFLAGS"])
 
+
+# Look for libgit2.
+PKG_CHECK_MODULES([LIBGIT2], [libgit2])
+
+
 # Setuid installations.
 AC_CHECK_FUNCS([setresuid setreuid lchown])
 

src/libfetchers/local.mk

@@ -8,6 +8,6 @@ libfetchers_SOURCES := $(wildcard $(d)/*.cc)
 
 libfetchers_CXXFLAGS += -I src/libutil -I src/libstore
 
-libfetchers_LDFLAGS += -pthread -lgit2 -larchive
+libfetchers_LDFLAGS += -pthread $(LIBGIT2_LIBS) -larchive
 
 libfetchers_LIBS = libutil libstore