configure: Add a comment indicating why uclibc is checked before glibc

diff --git a/configure b/configure
index c41a396..ebeea83 100755 (executable)
--- a/configure
+++ b/configure
@@ -3035,6 +3035,7 @@ esac
 
 # determine libc flavour
 
+# uclibc defines __GLIBC__, so it needs to be checked before glibc.
 if check_cpp_condition features.h "defined __UCLIBC__"; then
     libc_type=uclibc
     add_cppflags -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600