Merge bitcoin#518: Summarize build options after running configure

3965027 Summarize build options in configure script (Evan Klitzke)

Pull request description:

  This is a trivial build system change to summarize the build options after running configure.

  Example output:
  ```
  $ ./configure
  ....
  <many lines omitted>
  ...
  config.status: src/libsecp256k1-config.h is unchanged
  config.status: executing depfiles commands
  config.status: executing libtool commands

  Build Options:
    with endomorphism   = no
    with ecmult precomp = yes
    with jni            = no
    module ecdh         = no
    module recovery     = no

    asm                 = x86_64
    bignum              = gmp
    field               = 64bit
    scalar              = 64bit

    CC                  = gcc
    CFLAGS              = -g -O2 -W -std=c89 -pedantic -Wall -Wextra -Wcast-align -Wnested-externs -Wshadow -Wstrict-prototypes -Wno-unused-function -Wno-long-long -Wno-overlength-strings -fvisibility=hidden -O3
    CPPFLAGS            =
    LDFLAGS             =
  ```

  I tried to just include the configure options that looked interesting; let me know if there are any I didn't include that I should have.

Tree-SHA512: 428381654d772f76bc81210d39ba5c3f07a94dc6a6378a02ccc6f23ebce7f501896268bcd2e94e2b0d8aea54c9c70c44a9238a0f0960600f463b1e2847c7ed1f

configure.ac

@@ -435,18 +435,6 @@ if test x"$use_external_asm" = x"yes"; then
   AC_DEFINE(USE_EXTERNAL_ASM, 1, [Define this symbol if an external (non-inline) assembly implementation is used])
 fi
 
-AC_MSG_NOTICE([Using static precomputation: $set_precomp])
-AC_MSG_NOTICE([Using assembly optimizations: $set_asm])
-AC_MSG_NOTICE([Using field implementation: $set_field])
-AC_MSG_NOTICE([Using bignum implementation: $set_bignum])
-AC_MSG_NOTICE([Using scalar implementation: $set_scalar])
-AC_MSG_NOTICE([Using endomorphism optimizations: $use_endomorphism])
-AC_MSG_NOTICE([Building benchmarks: $use_benchmark])
-AC_MSG_NOTICE([Building for coverage analysis: $enable_coverage])
-AC_MSG_NOTICE([Building ECDH module: $enable_module_ecdh])
-AC_MSG_NOTICE([Building ECDSA pubkey recovery module: $enable_module_recovery])
-AC_MSG_NOTICE([Using jni: $use_jni])
-
 if test x"$enable_experimental" = x"yes"; then
   AC_MSG_NOTICE([******])
   AC_MSG_NOTICE([WARNING: experimental build])
@@ -486,3 +474,24 @@ unset PKG_CONFIG_PATH
 PKG_CONFIG_PATH="$PKGCONFIG_PATH_TEMP"
 
 AC_OUTPUT
+
+echo
+echo "Build Options:"
+echo "  with endomorphism   = $use_endomorphism"
+echo "  with ecmult precomp = $set_precomp"
+echo "  with jni            = $use_jni"
+echo "  with benchmarks     = $use_benchmark"
+echo "  with coverage       = $enable_coverage"
+echo "  module ecdh         = $enable_module_ecdh"
+echo "  module recovery     = $enable_module_recovery"
+echo
+echo "  asm                 = $set_asm"
+echo "  bignum              = $set_bignum"
+echo "  field               = $set_field"
+echo "  scalar              = $set_scalar"
+echo
+echo "  CC                  = $CC"
+echo "  CFLAGS              = $CFLAGS"
+echo "  CPPFLAGS            = $CPPFLAGS"
+echo "  LDFLAGS             = $LDFLAGS"
+echo