Replace statvfs64 with statvfs and define _FILE_OFFSET_BITS=64.

On my musl system statvfs64 is not exposed by default. The musl FAQ
recommends against using type64_t types, see:
https://wiki.musl-libc.org/faq.html#Q:-Do-I-need-to-define-%3Ccode%3E_LARGEFILE64_SOURCE%3C/code%3E-to-get-64bit-%3Ccode%3Eoff_t%3C/code%3E?.

Defining `_FILE_OFFSET_BITS=64` and using type_t lets type_t use the 64
bit interface, see:
https://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html#index-_005fFILE_005fOFFSET_005fBITS.

Makefile

@@ -131,7 +131,7 @@ override GOODFLAGS := $(foreach flag,$(TESTFLAGS),$(strip $(shell echo "int main
 override REQFLAGS   := -std=c++20
 WARNFLAGS			:= -Wall -Wextra -pedantic
 OPTFLAGS			:= -O2 -ftree-vectorize -flto=$(THREADS)
-LDCXXFLAGS			:= -pthread -D_FORTIFY_SOURCE=2 -D_GLIBCXX_ASSERTIONS $(GOODFLAGS) $(ADDFLAGS)
+LDCXXFLAGS			:= -pthread -D_FORTIFY_SOURCE=2 -D_GLIBCXX_ASSERTIONS -D_FILE_OFFSET_BITS=64 $(GOODFLAGS) $(ADDFLAGS)
 override CXXFLAGS	+= $(REQFLAGS) $(LDCXXFLAGS) $(OPTFLAGS) $(WARNFLAGS)
 override LDFLAGS	+= $(LDCXXFLAGS) $(OPTFLAGS) $(WARNFLAGS)
 INC					:= -I$(INCDIR) -I$(SRCDIR)

src/linux/btop_collect.cpp

@@ -1083,9 +1083,9 @@ namespace Mem {
 				bool new_ignored = false;
 				for (auto& [mountpoint, disk] : disks) {
 					if (std::error_code ec; not fs::exists(mountpoint, ec) or v_contains(ignore_list, mountpoint)) continue;
-					struct statvfs64 vfs;
-					if (statvfs64(mountpoint.c_str(), &vfs) < 0) {
-						Logger::warning("Failed to get disk/partition stats for mount \""+ mountpoint + "\" with statvfs64 error code: " + to_string(errno) + ". Ignoring...");
+					struct statvfs vfs;
+					if (statvfs(mountpoint.c_str(), &vfs) < 0) {
+						Logger::warning("Failed to get disk/partition stats for mount \""+ mountpoint + "\" with statvfs error code: " + to_string(errno) + ". Ignoring...");
 						ignore_list.push_back(mountpoint);
 						new_ignored = true;
 						continue;