Long live qbs-pkgconfig!

This patchset introduce a static library for parsing .pc files. Code is
based on the original pkg-config source code https://
gitlab.freedesktop.org/pkg-config/pkg-config and is written in pure C++
(except for the places where we need access to filesystem as
std::filesystem is not available for all platforms - in that case, Qt
classes are used)

Parsing .pc files manually allows to have more control over dependencies
between modules, e.g. to generate a standalone module per one .pc file
and merge properties using Qbs itself, not via pkg-config.

Library is almost feature-complete and all tests copied from pkg-config
pass. Some functionality is omitted (e.g. prefix variables (what is
this?) or validating dependencies since Qbs does this as well)

Bechmark shows that parsing ~100 files takes about 10-15ms. Running
pkg-config on the same set of files takes ~4 seconds:

RESULT : TestPkgConfig::benchSystem():
     14 msecs per iteration (total: 57, iterations: 4)

Fixes: QBS-1615
Change-Id: I5bfdfa588aa04d9d69fd738dd2beea14174c0242
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/auto/pkgconfig/testdata/system.pc b/tests/auto/pkgconfig/testdata/system.pc
new file mode 100644
index 000000000..2cef2ed9b
--- /dev/null
+++ b/tests/auto/pkgconfig/testdata/system.pc
@@ -0,0 +1,10 @@
+prefix=/usr
+exec_prefix=${prefix}
+libdir=${exec_prefix}/lib
+includedir=${prefix}/include
+
+Name: System library
+Description: Test package
+Version: 1.0.0
+Libs: -L${libdir} -lsystem
+Cflags: -I${includedir}