Merge bitcoin-core/secp256k1#1088: configure: Use modern way to set AR

0d253d5 configure: Use modern way to set AR (Tim Ruffing)

Pull request description:

ACKs for top commit:
  jb55:
    tACK 0d253d5
  hebasto:
    ACK 0d253d5
  jonasnick:
    ACK 0d253d5

Tree-SHA512: c85a068b0b6cd0ae59c796d4493d50b1d92394b8620dd65affb5aaac889a41aa625408062f49fbed761217ab2bc35ec10942684a84487cb81becdadf5f2ae2af

.gitignore

@@ -46,6 +46,7 @@ coverage.*.html
 
 src/libsecp256k1-config.h
 src/libsecp256k1-config.h.in
+build-aux/ar-lib
 build-aux/config.guess
 build-aux/config.sub
 build-aux/depcomp

configure.ac

@@ -25,24 +25,23 @@ AC_CANONICAL_HOST
 AH_TOP([#ifndef LIBSECP256K1_CONFIG_H])
 AH_TOP([#define LIBSECP256K1_CONFIG_H])
 AH_BOTTOM([#endif /*LIBSECP256K1_CONFIG_H*/])
-AM_INIT_AUTOMAKE([foreign subdir-objects])
 
-LT_INIT([win32-dll])
+# Require Automake 1.11.2 for AM_PROG_AR
+AM_INIT_AUTOMAKE([1.11.2 foreign subdir-objects])
 
 # Make the compilation flags quiet unless V=1 is used.
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
 PKG_PROG_PKG_CONFIG
 
-AC_PATH_TOOL(AR, ar)
-AC_PATH_TOOL(RANLIB, ranlib)
-AC_PATH_TOOL(STRIP, strip)
-
 AC_PROG_CC
 if test x"$ac_cv_prog_cc_c89" = x"no"; then
   AC_MSG_ERROR([c89 compiler support required])
 fi
 AM_PROG_AS
+AM_PROG_AR
+
+LT_INIT([win32-dll])
 
 build_windows=no