Make bzip2 unit tests pass on musl-based systems

Other than glibc, the musl standard C library does not check the
validity of file descriptors passed to `fdopen()`, so the constructor
of the (de)compressor does not throw an excption on musl-based systems.
Rather, an exception is thrown later, when the opened file is being used.
According to the musl team, the current musl behavior conforms to the POSIX
specification, and application code should be made agnostic to whether
or not the standard C library happens to validate file descriptors
passed to `fdopen()`.

For the discussion of `fdopen()` filedescriptor validation, see this
thread on the musl mailing list:

* https://www.openwall.com/lists/musl/2022/08/04/1
* https://www.openwall.com/lists/musl/2022/08/04/2
* https://www.openwall.com/lists/musl/2022/08/04/3

After this change, all libosmium tests (including those for bzip2) are
passing on Alpine Linux, which uses musl as its standard C library.

Fixes #353.

Author: brawer

test/t/io/test_bzip2.cpp

@@ -7,13 +7,19 @@
 
 #include <string>
 
+static void read_from_decompressor(int fd) {
+    osmium::io::Bzip2Decompressor decomp{fd};
+    decomp.read();
+    decomp.close();
+}
+
 TEST_CASE("Invalid file descriptor of bzip2-compressed file") {
-    REQUIRE_THROWS_AS(osmium::io::Bzip2Decompressor{-1}, std::system_error);
+    REQUIRE_THROWS(read_from_decompressor(-1));
 }
 
 TEST_CASE("Non-open file descriptor of bzip2-compressed file") {
     // 12345 is just a random file descriptor that should not be open
-    REQUIRE_THROWS_AS(osmium::io::Bzip2Decompressor{12345}, std::system_error);
+    REQUIRE_THROWS(read_from_decompressor(12345));
 }
 
 TEST_CASE("Empty bzip2-compressed file") {
@@ -93,13 +99,19 @@ TEST_CASE("Corrupted bzip2-compressed file") {
     REQUIRE(count == count_fds());
 }
 
+static void write_to_compressor(int fd) {
+    osmium::io::Bzip2Compressor comp{fd, osmium::io::fsync::yes};
+    comp.write("foo");
+    comp.close();
+}
+
 TEST_CASE("Compressor: Invalid file descriptor for bzip2-compressed file") {
-    REQUIRE_THROWS_AS(osmium::io::Bzip2Compressor(-1, osmium::io::fsync::yes), std::system_error);
+    REQUIRE_THROWS(write_to_compressor(-1));
 }
 
 TEST_CASE("Compressor: Non-open file descriptor for bzip2-compressed file") {
     // 12345 is just a random file descriptor that should not be open
-    REQUIRE_THROWS_AS(osmium::io::Bzip2Compressor(12345, osmium::io::fsync::yes), std::system_error);
+    REQUIRE_THROWS(write_to_compressor(12345));
 }
 
 TEST_CASE("Write bzip2-compressed file with explicit close") {