configure: grab CPPFLAGS from the environment.

This is needed in particular for hardening flags.

diff --git a/configure b/configure
index 460fcfcf31178ea4b1ecdf9fc506e692b064747a..3ba1ec3497419409045a7afc4b4cb4c37f0677e1 100755 (executable)
--- a/configure
+++ b/configure
@@ -43,6 +43,7 @@ fi
 CC=${CC:-gcc}
 CXX=${CXX:-g++}
 CFLAGS=${CFLAGS:--O2}
+CPPFLAGS=${CPPFLAGS:-}
 CXXFLAGS=${CXXFLAGS:-\$(CFLAGS)}
 LDFLAGS=${LDFLAGS:-}
 XAPIAN_CONFIG=${XAPIAN_CONFIG:-xapian-config}
@@ -91,6 +92,7 @@ First, some common variables can specified via environment variables:
 
        CC              The C compiler to use
        CFLAGS          Flags to pass to the C compiler
+        CPPFLAGS       Flags to pass to the C preprocessor
        CXX             The C++ compiler to use
        CXXFLAGS        Flags to pass to the C compiler
        LDFLAGS         Flags to pass when linking
@@ -615,6 +617,9 @@ EMACS = emacs --quick
 # Default FLAGS for C compiler (can be overridden by user such as "make CFLAGS=-g")
 CFLAGS = ${CFLAGS}
 
+# Default FLAGS for C preprocessor (can be overridden by user such as "make CPPFLAGS=-I/usr/local/include")
+CPPFLAGS = ${CPPFLAGS}
+
 # Default FLAGS for C++ compiler (can be overridden by user such as "make CXXFLAGS=-g")
 CXXFLAGS = ${CXXFLAGS}