configure: wrap some library tests with GIT_STASH_FLAGS

Libraries that can have user specificed base paths are wrapped with
GIT_STASH_FLAGS/GIT_UNSTASH_FLAGS to ensure that the proper versions
on the system are tested.  This ensures, for example, that the zlib
tests for deflateUnbound are done with the version of zlib requested
by the user.  This is most useful in the absence of good settings for
CPPFLAGS and/or LDFLAGS.

Signed-off-by: Ben Walton <bwalton@artsci.utoronto.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

configure.ac

@@ -315,33 +315,57 @@ AC_MSG_NOTICE([CHECKS for libraries])
 #
 # Define NO_OPENSSL environment variable if you do not have OpenSSL.
 # Define NEEDS_SSL_WITH_CRYPTO if you need -lcrypto with -lssl (Darwin).
+
+GIT_STASH_FLAGS($OPENSSLDIR)
+
 AC_CHECK_LIB([crypto], [SHA1_Init],
 [NEEDS_SSL_WITH_CRYPTO=],
 [AC_CHECK_LIB([ssl], [SHA1_Init],
  [NEEDS_SSL_WITH_CRYPTO=YesPlease
   NEEDS_SSL_WITH_CRYPTO=],
  [NO_OPENSSL=YesPlease])])
+
+GIT_UNSTASH_FLAGS($OPENSSLDIR)
+
 AC_SUBST(NEEDS_SSL_WITH_CRYPTO)
 AC_SUBST(NO_OPENSSL)
+
 #
 # Define NO_CURL if you do not have libcurl installed.  git-http-pull and
 # git-http-push are not built, and you cannot use http:// and https://
 # transports.
+
+GIT_STASH_FLAGS($CURLDIR)
+
 AC_CHECK_LIB([curl], [curl_global_init],
 [NO_CURL=],
 [NO_CURL=YesPlease])
+
+GIT_UNSTASH_FLAGS($CURLDIR)
+
 AC_SUBST(NO_CURL)
+
 #
 # Define NO_EXPAT if you do not have expat installed.  git-http-push is
 # not built, and you cannot push using http:// and https:// transports.
+
+GIT_STASH_FLAGS($EXPATDIR)
+
 AC_CHECK_LIB([expat], [XML_ParserCreate],
 [NO_EXPAT=],
 [NO_EXPAT=YesPlease])
+
+GIT_UNSTASH_FLAGS($EXPATDIR)
+
 AC_SUBST(NO_EXPAT)
+
 #
 # Define NEEDS_LIBICONV if linking with libc is not enough (Darwin and
 # some Solaris installations).
 # Define NO_ICONV if neither libc nor libiconv support iconv.
+
+GIT_STASH_FLAGS($ICONVDIR)
+
 AC_DEFUN([ICONVTEST_SRC], [
 #include <iconv.h>
 
@@ -365,11 +389,17 @@ AC_LINK_IFELSE(ICONVTEST_SRC,
 		[AC_MSG_RESULT([no])
 		NO_ICONV=YesPlease])
 	LIBS="$old_LIBS"])
+
+GIT_UNSTASH_FLAGS($ICONVDIR)
+
 AC_SUBST(NEEDS_LIBICONV)
 AC_SUBST(NO_ICONV)
-test -n "$NEEDS_LIBICONV" && LIBS="$LIBS -liconv"
+
 #
 # Define NO_DEFLATE_BOUND if deflateBound is missing from zlib.
+
+GIT_STASH_FLAGS($ZLIB_PATH)
+
 AC_DEFUN([ZLIBTEST_SRC], [
 #include <zlib.h>
 
@@ -387,7 +417,11 @@ AC_LINK_IFELSE(ZLIBTEST_SRC,
 	[AC_MSG_RESULT([no])
 	NO_DEFLATE_BOUND=yes])
 LIBS="$old_LIBS"
+
+GIT_UNSTASH_FLAGS($ZLIB_PATH)
+
 AC_SUBST(NO_DEFLATE_BOUND)
+
 #
 # Define NEEDS_SOCKET if linking with libc is not enough (SunOS,
 # Patrick Mauritz).