Test for C++ pch.

test cases/14 cxx pch/builder.txt

@@ -0,0 +1,3 @@
+project('c++ pch test', 'c++')
+exe = executable('prog', 'prog.cc')
+exe.pch('pch/prog.hh')

test cases/14 cxx pch/pch/prog.hh

@@ -0,0 +1 @@
+#include<iostream>

test cases/14 cxx pch/prog.cc

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+void func() {
+    std::cout << "This is a function that fails to compile if iostream is not included."
+              << std::endl;
+}
+
+int main(int argc, char **argv) {
+    return 0;
+}