a58868d201 build: Makes rcc output always deterministic (Hennadii Stepanov)
Pull request description:
The Qt Resource Compiler ([rcc](https://doc.qt.io/qt-5/rcc.html)) has a command-line option `--format-version` which has the [default value](https://code.qt.io/cgit/qt/qtbase.git/tree/src/tools/rcc/main.cpp?h=5.12.10#n172) 2.
The only difference from `--format-version 1` is adding a [last modified timestamp](https://code.qt.io/cgit/qt/qtbase.git/tree/src/tools/rcc/rcc.cpp?h=5.12.10#n207) to the output file ([credits](https://github.com/bitcoin/bitcoin/pull/21654#issuecomment-819198228) to **fanquake**). That, in turn, forces us to use `QT_RCC_SOURCE_DATE_OVERRIDE=1` to get deterministic builds (#13732).
This change makes rcc output always deterministic by using `--format-version 1` option that makes usage of the
`QT_RCC_SOURCE_DATE_OVERRIDE` needless.
---
Also it improves interaction with ccache:
On master (f6c44e999b):
```
$ make && make clean && ccache --zero-stats && make && ccache --show-stats
...
cache directory /home/hebasto/.ccache
primary config /home/hebasto/.ccache/ccache.conf
secondary config (readonly) /etc/ccache.conf
stats updated Sun Apr 11 15:45:43 2021
stats zeroed Sun Apr 11 15:45:05 2021
cache hit (direct) 638
cache hit (preprocessed) 0
cache miss 1
cache hit rate 99.84 %
called for link 10
cleanups performed 0
files in cache 20023
cache size 13.2 GB
max cache size 15.0 GB
```
The missed file is always `qt/libbitcoinqt_a-qrc_bitcoin_locale.o`.
With this PR:
```
$ make && make clean && ccache --zero-stats && make && ccache --show-stats
...
cache directory /home/hebasto/.ccache
primary config /home/hebasto/.ccache/ccache.conf
secondary config (readonly) /etc/ccache.conf
stats updated Sun Apr 11 15:28:46 2021
stats zeroed Sun Apr 11 15:28:21 2021
cache hit (direct) 639
cache hit (preprocessed) 0
cache miss 0
cache hit rate 100.00 %
called for link 10
cleanups performed 0
files in cache 20012
cache size 13.2 GB
max cache size 15.0 GB
```
ACKs for top commit:
fanquake:
ACK a58868d201
Tree-SHA512: 52f4a3267f41883d13025c0de79b6da22e92d60c729e01b986935c6812bbfe7fadc40b742bd715bfdf09df94af6838d4fbbe8208c6123f366108e38c8e1121c5
8837f1ebde