Auto merge of #2786 - str4d:2074-build, r=str4d

Build system improvements

Includes commits cherry-picked from the following upstream PRs:

- bitcoin/bitcoin#6978
  - Only the first commit (second is for QT)
- bitcoin/bitcoin#7059
- bitcoin/bitcoin#7603
  - Only the first commit (without the `BITCOIN_QT_BIN` variable; the rest are for QT)
- bitcoin/bitcoin#7954
- bitcoin/bitcoin#8314
  - Only the second commit (first is for QT)
- bitcoin/bitcoin#8504
  - Only the first commit (second was undoing something we didn't have)
- bitcoin/bitcoin#8520
- bitcoin/bitcoin#8563
- bitcoin/bitcoin#8249
- bitcoin/bitcoin#9156
- bitcoin/bitcoin#9831
- bitcoin/bitcoin#9789
- bitcoin/bitcoin#10766

Part of #2074.

zcutil/build.sh

@@ -132,5 +132,5 @@ ld -v
 
 HOST="$HOST" BUILD="$BUILD" NO_RUST="$RUST_ARG" NO_PROTON="$PROTON_ARG" "$MAKE" "$@" -C ./depends/ V=1
 ./autogen.sh
-CC="$CC" CXX="$CXX" ./configure --prefix="${PREFIX}" --host="$HOST" --build="$BUILD" "$RUST_ARG" "$HARDENING_ARG" "$LCOV_ARG" "$TEST_ARG" "$MINING_ARG" "$PROTON_ARG" "$LIBS_ARG" CXXFLAGS='-fwrapv -fno-strict-aliasing -Wno-builtin-declaration-mismatch -Werror -g'
+CC="$CC" CXX="$CXX" ./configure --prefix="${PREFIX}" --host="$HOST" --build="$BUILD" "$RUST_ARG" "$HARDENING_ARG" "$LCOV_ARG" "$TEST_ARG" "$MINING_ARG" "$PROTON_ARG" "$LIBS_ARG" --enable-werror CXXFLAGS='-g'
 "$MAKE" "$@" V=1