RFR (S): JDK-8027300 configure should use LIBS instead of LDFLAGS when testing freetype

[Magnus Ihse Bursie]

Bug: https://bugs.openjdk.java.net/browse/JDK-8027300

When testing if linking with freetype works, link flags order are 
important for newer gcc.

The freetype library flags must be added to LIBS, not LDFLAGS, for 
linking to succeed on newer gcc's.

WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8027300-use-LIBS-when-checking-freetype/webrev.01

/Magnus