--- a/usr/portage/eclass/qt5-build.eclass	2018-01-19 11:33:04.373616500 +0100
+++ b/usr/portage/eclass/qt5-build.eclass	2018-01-19 11:40:39.881565600 +0100
@@ -321,6 +321,14 @@
 
 	qt5_install_module_qconfigs
 	prune_libtool_files
+
+	# There is no way to teach the build system to play nicely
+	# with the slightly different directory layout on cygwin.
+	# Note: cygwinports does it like that, too.
+	if use elibc_Cygwin; then
+		dodir /usr/bin
+		mv "${D}"$EPREFIX/usr/lib/*.dll "${D}"$EPREFIX/usr/bin/
+	fi
 }
 
 # @FUNCTION: qt5-build_pkg_postinst
@@ -699,7 +707,7 @@
 # @DESCRIPTION:
 # Helper function to get the various toolchain-related variables.
 qt5_qmake_args() {
-	echo \
+	echo -n \
 		QMAKE_AR=\"$(tc-getAR)\" \
 		QMAKE_CC=\"$(tc-getCC)\" \
 		QMAKE_LINK_C=\"$(tc-getCC)\" \
@@ -710,15 +718,26 @@
 		QMAKE_OBJCOPY=\"$(tc-getOBJCOPY)\" \
 		QMAKE_RANLIB= \
 		QMAKE_STRIP=\"$(tc-getSTRIP)\" \
-		QMAKE_CFLAGS=\"${CFLAGS}\" \
 		QMAKE_CFLAGS_RELEASE= \
 		QMAKE_CFLAGS_DEBUG= \
-		QMAKE_CXXFLAGS=\"${CXXFLAGS}\" \
 		QMAKE_CXXFLAGS_RELEASE= \
 		QMAKE_CXXFLAGS_DEBUG= \
-		QMAKE_LFLAGS=\"${LDFLAGS}\" \
 		QMAKE_LFLAGS_RELEASE= \
 		QMAKE_LFLAGS_DEBUG=
+	if use elibc_Cygwin; then
+		# The specs for cygwin add some crucial FLAGS that must not
+		# be thrown away. Better add the environment flags, so the
+		# specs flags can still be overridden.
+		echo \
+			QMAKE_CFLAGS+=\"${CFLAGS}\" \
+			QMAKE_CXXFLAGS+=\"${CXXFLAGS}\" \
+			QMAKE_LFLAGS+=\"${LDFLAGS}\"
+	else
+		echo \
+			QMAKE_CFLAGS=\"${CFLAGS}\" \
+			QMAKE_CXXFLAGS=\"${CXXFLAGS}\" \
+			QMAKE_LFLAGS=\"${LDFLAGS}\"
+	fi
 }
 
 # @FUNCTION: qt5_qmake
@@ -729,11 +748,26 @@
 qt5_qmake() {
 	local projectdir=${PWD/#${QT5_BUILD_DIR}/${S}}
 	local qmakepath=
+	local qmakeopts=(
+		QMAKE_CFLAGS=\"${CFLAGS}\"
+		QMAKE_CXXFLAGS=\"${CXXFLAGS}\"
+		QMAKE_LFLAGS=\"${LDFLAGS}\"
+	)
 	if [[ ${QT5_MODULE} == qtbase ]]; then
 		qmakepath=${QT5_BUILD_DIR}/bin
 	else
 		qmakepath=${QT5_BINDIR}
 	fi
+	if use elibc_Cygwin; then
+		# The specs for cygwin add some crucial FLAGS that must not
+		# be thrown away. Better add the environment flags, so the
+		# specs flags can still be overridden.
+		qmakeopts=(
+			QMAKE_CFLAGS+=\"${CFLAGS}\"
+			QMAKE_CXXFLAGS+=\"${CXXFLAGS}\"
+			QMAKE_LFLAGS+=\"${LDFLAGS}\"
+		)
+	fi
 
 	"${qmakepath}"/qmake \
 		"${projectdir}" \
@@ -749,15 +783,13 @@
 		QMAKE_OBJCOPY="$(tc-getOBJCOPY)" \
 		QMAKE_RANLIB= \
 		QMAKE_STRIP="$(tc-getSTRIP)" \
-		QMAKE_CFLAGS="${CFLAGS}" \
 		QMAKE_CFLAGS_RELEASE= \
 		QMAKE_CFLAGS_DEBUG= \
-		QMAKE_CXXFLAGS="${CXXFLAGS}" \
 		QMAKE_CXXFLAGS_RELEASE= \
 		QMAKE_CXXFLAGS_DEBUG= \
-		QMAKE_LFLAGS="${LDFLAGS}" \
 		QMAKE_LFLAGS_RELEASE= \
 		QMAKE_LFLAGS_DEBUG= \
+		"${qmakeopts[@]}" \
 		"${myqmakeargs[@]}" \
 		|| die "qmake failed (${projectdir#${S}/})"
 }