New review comment by sgn on void-packages repository

https://github.com/void-linux/void-packages/pull/28304#discussion_r567353558

Comment:
`configure_args+'" -G'Unix Makefiles'"` doesn't work.

> CMake Error: Could not create named generator 'Unix

I think we're better to do this instead:
```diff
diff --git a/common/build-style/cmake.sh b/common/build-style/cmake.sh
index 6078ede1f4..26d55f527e 100644
--- a/common/build-style/cmake.sh
+++ b/common/build-style/cmake.sh
@@ -62,9 +62,10 @@ _EOF
 
 	cmake_args+=" -DCMAKE_INSTALL_SBINDIR=bin"
 
+	export CMAKE_GENERATOR="${CMAKE_GENERATOR:-Ninja}"
 	# Override flags: https://gitlab.kitware.com/cmake/cmake/issues/19590
 	CFLAGS="${CFLAGS/ -pipe / }" CXXFLAGS="${CXXFLAGS/ -pipe / }" \
-		cmake ${cmake_args} -GNinja ${configure_args} ${wrksrc}/${build_wrksrc}
+		cmake ${cmake_args} ${configure_args} ${wrksrc}/${build_wrksrc}
 
 	# Replace -isystem with -I for Qt4 and Qt5 packages
 	find -name flags.make -exec sed -i "{}" -e"s;-isystem;-I;g" \;
diff --git a/srcpkgs/ccache/template b/srcpkgs/ccache/template
index 52e60be6fc..9f42aa4731 100644
--- a/srcpkgs/ccache/template
+++ b/srcpkgs/ccache/template
@@ -16,7 +16,7 @@ checksum=5fdc804056632d722a1182e15386696f0ea6c59cb4ab4d65a54f0b269ae86f99
 
 if [ -z "$CHROOT_READY" ]; then
 	hostmakedepends="cmake-bootstrap"
-	configure_args+=" -G'Unix Makefiles'"
+	export CMAKE_GENERATOR="Unix Makefiles"
 	make_cmd="make"
 else
 	hostmakedepends="asciidoc perl"
diff --git a/srcpkgs/cmake/template b/srcpkgs/cmake/template
index e3e59a31fb..cb351b5b75 100644
--- a/srcpkgs/cmake/template
+++ b/srcpkgs/cmake/template
@@ -17,6 +17,8 @@ homepage="https://www.cmake.org"
 distfiles="https://www.cmake.org/files/v${version%.*}/${pkgname}-${version}.tar.gz"
 checksum=7d0232b9f1c57e8de81f38071ef8203e6820fe7eec8ae46a1df125d88dbcc2e1
 
+export CMAKE_GENERATOR="Unix Makefiles"
+
 pre_check() {
 	# use ctest of this build instead of requirig cmake to test cmake...
 	vsed -i "${wrksrc}/build/Makefile" \
```